// File: @yield-protocol/yieldspace-v2/contracts/Pool.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity 0.8.6;

import "@yield-protocol/utils-v2/contracts/token/IERC20.sol";
import "@yield-protocol/utils-v2/contracts/token/IERC20Metadata.sol";
import "@yield-protocol/utils-v2/contracts/token/ERC20Permit.sol";
import "@yield-protocol/utils-v2/contracts/token/MinimalTransferHelper.sol";
import "@yield-protocol/utils-v2/contracts/cast/CastU256U128.sol";
import "@yield-protocol/utils-v2/contracts/cast/CastU256U112.sol";
import "@yield-protocol/utils-v2/contracts/cast/CastU256I256.sol";
import "@yield-protocol/utils-v2/contracts/cast/CastU128U112.sol";
import "@yield-protocol/utils-v2/contracts/cast/CastU128I128.sol";
import "@yield-protocol/yieldspace-interfaces/IPool.sol";
import "@yield-protocol/vault-interfaces/IFYToken.sol";
import "./YieldMath.sol";


/// @dev The Pool contract exchanges base for fyToken at a price defined by a specific formula.
contract Pool is IPool, ERC20Permit {
    using CastU256U128 for uint256;
    using CastU256U112 for uint256;
    using CastU256I256 for uint256;
    using CastU128U112 for uint128;
    using CastU128I128 for uint128;
    using MinimalTransferHelper for IERC20;

    event Trade(uint32 maturity, address indexed from, address indexed to, int256 bases, int256 fyTokens);
    event Liquidity(uint32 maturity, address indexed from, address indexed to, address indexed fyTokenTo, int256 bases, int256 fyTokens, int256 poolTokens);
    event Sync(uint112 baseCached, uint112 fyTokenCached, uint256 cumulativeBalancesRatio);

    int128 public immutable override ts;              // 1 / Seconds in 10 years, in 64.64
    int128 public immutable override g1;             // To be used when selling base to the pool
    int128 public immutable override g2;             // To be used when selling fyToken to the pool
    uint32 public immutable override maturity;
    uint96 public immutable override scaleFactor;    // Scale up to 18 low decimal tokens to get the right precision in YieldMath

    IERC20 public immutable override base;
    IFYToken public immutable override fyToken;

    uint112 private baseCached;              // uses single storage slot, accessible via getCache
    uint112 private fyTokenCached;           // uses single storage slot, accessible via getCache
    uint32  private blockTimestampLast;      // uses single storage slot, accessible via getCache

    uint256 public cumulativeBalancesRatio;  // Fixed point factor with 27 decimals (ray)

    /// @dev Deploy a Pool.
    /// Make sure that the fyToken follows ERC20 standards with regards to name, symbol and decimals
    constructor(IERC20 base_, IFYToken fyToken_, int128 ts_, int128 g1_, int128 g2_)
        ERC20Permit(
            string(abi.encodePacked(IERC20Metadata(address(fyToken_)).name(), " LP")),
            string(abi.encodePacked(IERC20Metadata(address(fyToken_)).symbol(), "LP")),
            IERC20Metadata(address(fyToken_)).decimals()
        )
    {
        fyToken = fyToken_;
        base = base_;

        uint256 maturity_ = fyToken_.maturity();
        require (maturity_ <= type(uint32).max, "Pool: Maturity too far in the future");
        maturity = uint32(maturity_);

        ts = ts_;
        g1 = g1_;
        g2 = g2_;

        scaleFactor = uint96(10 ** (18 - uint96(decimals)));
    }

    /// @dev Trading can only be done before maturity
    modifier beforeMaturity() {
        require(
            block.timestamp < maturity,
            "Pool: Too late"
        );
        _;
    }

    // ---- Balances management ----

    /// @dev Updates the cache to match the actual balances.
    function sync() external {
        _update(_getBaseBalance(), _getFYTokenBalance(), baseCached, fyTokenCached);
    }

    /// @dev Returns the cached balances & last updated timestamp.
    /// @return Cached base token balance.
    /// @return Cached virtual FY token balance.
    /// @return Timestamp that balances were last cached.
    function getCache()
        external view override
        returns (uint112, uint112, uint32)
    {
        return (baseCached, fyTokenCached, blockTimestampLast);
    }

    /// @dev Returns the "virtual" fyToken balance, which is the real balance plus the pool token supply.
    function getFYTokenBalance()
        public view override
        returns(uint112)
    {
        return _getFYTokenBalance();
    }

    /// @dev Returns the base balance
    function getBaseBalance()
        public view override
        returns(uint112)
    {
        return _getBaseBalance();
    }

    /// @dev Returns the "virtual" fyToken balance, which is the real balance plus the pool token supply.
    function _getFYTokenBalance()
        internal view
        returns(uint112)
    {
        return (fyToken.balanceOf(address(this)) + _totalSupply).u112();
    }

    /// @dev Returns the base balance
    function _getBaseBalance()
        internal view
        returns(uint112)
    {
        return base.balanceOf(address(this)).u112();
    }

    /// @dev Retrieve any base tokens not accounted for in the cache
    function retrieveBase(address to)
        external override
        returns(uint128 retrieved)
    {
        retrieved = _getBaseBalance() - baseCached; // Cache can never be above balances
        base.safeTransfer(to, retrieved);
        // Now the current balances match the cache, so no need to update the TWAR
    }

    /// @dev Retrieve any fyTokens not accounted for in the cache
    function retrieveFYToken(address to)
        external override
        returns(uint128 retrieved)
    {
        retrieved = _getFYTokenBalance() - fyTokenCached; // Cache can never be above balances
        IERC20(address(fyToken)).safeTransfer(to, retrieved);
        // Now the balances match the cache, so no need to update the TWAR
    }

    /// @dev Update cache and, on the first call per block, ratio accumulators
    function _update(uint128 baseBalance, uint128 fyBalance, uint112 _baseCached, uint112 _fyTokenCached) private {
        uint32 blockTimestamp = uint32(block.timestamp);
        uint32 timeElapsed = blockTimestamp - blockTimestampLast; // overflow is desired
        if (timeElapsed > 0 && _baseCached != 0 && _fyTokenCached != 0) {
            // We multiply by 1e27 here so that r = t * y/x is a fixed point factor with 27 decimals 
            uint256 scaledFYTokenCached = uint256(_fyTokenCached) * 1e27;
            cumulativeBalancesRatio += scaledFYTokenCached  * timeElapsed / _baseCached;
        }
        baseCached = baseBalance.u112();
        fyTokenCached = fyBalance.u112();
        blockTimestampLast = blockTimestamp;
        emit Sync(baseCached, fyTokenCached, cumulativeBalancesRatio);
    }

    // ---- Liquidity ----

    /// @dev Mint liquidity tokens in exchange for adding base and fyToken
    /// The amount of liquidity tokens to mint is calculated from the amount of unaccounted for fyToken in this contract.
    /// A proportional amount of base tokens need to be present in this contract, also unaccounted for.
    /// @param to Wallet receiving the minted liquidity tokens.
    /// @param remainder Wallet receiving any surplus base.
    /// @param minRatio Minimum ratio of base to fyToken in the pool.
    /// @param maxRatio Maximum ratio of base to fyToken in the pool.
    /// @return The amount of liquidity tokens minted.
    function mint(address to, address remainder, uint256 minRatio, uint256 maxRatio)
        external override
        returns (uint256, uint256, uint256)
    {
        return _mintInternal(to, remainder, 0, minRatio, maxRatio);
    }

    /// @dev Mint liquidity tokens in exchange for adding only base
    /// The amount of liquidity tokens is calculated from the amount of fyToken to buy from the pool,
    /// plus the amount of unaccounted for fyToken in this contract.
    /// The base tokens need to be present in this contract, unaccounted for.
    /// @param to Wallet receiving the minted liquidity tokens.
    /// @param remainder Wallet receiving any surplus base.
    /// @param fyTokenToBuy Amount of `fyToken` being bought in the Pool, from this we calculate how much base it will be taken in.
    /// @param minRatio Minimum ratio of base to fyToken in the pool.
    /// @param maxRatio Maximum ratio of base to fyToken in the pool.
    /// @return The amount of liquidity tokens minted.
    function mintWithBase(address to, address remainder, uint256 fyTokenToBuy, uint256 minRatio, uint256 maxRatio)
        external override
        returns (uint256, uint256, uint256)
    {
        return _mintInternal(to, remainder, fyTokenToBuy, minRatio, maxRatio);
    }

    /// @dev Mint liquidity tokens, with an optional internal trade to buy fyToken beforehand.
    /// The amount of liquidity tokens is calculated from the amount of fyToken to buy from the pool,
    /// plus the amount of unaccounted for fyToken in this contract.
    /// The base tokens need to be present in this contract, unaccounted for.
    /// @param to Wallet receiving the minted liquidity tokens.
    /// @param remainder Wallet receiving any surplus base.
    /// @param fyTokenToBuy Amount of `fyToken` being bought in the Pool, from this we calculate how much base it will be taken in.
    /// @param minRatio Minimum ratio of base to fyToken in the pool.
    /// @param maxRatio Minimum ratio of base to fyToken in the pool.
    function _mintInternal(address to, address remainder, uint256 fyTokenToBuy, uint256 minRatio, uint256 maxRatio)
        internal
        returns (uint256 baseIn, uint256 fyTokenIn, uint256 tokensMinted)
    {
        // Gather data
        uint256 supply = _totalSupply;
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        uint256 _realFYTokenCached = _fyTokenCached - supply;    // The fyToken cache includes the virtual fyToken, equal to the supply
        uint256 baseBalance = base.balanceOf(address(this));
        uint256 fyTokenBalance = fyToken.balanceOf(address(this));
        uint256 baseAvailable = baseBalance - _baseCached;

        // Check the burn wasn't sandwiched
        require (
            _realFYTokenCached == 0 || (
                uint256(_baseCached) * 1e18 / _realFYTokenCached >= minRatio &&
                uint256(_baseCached) * 1e18 / _realFYTokenCached <= maxRatio
            ),
            "Pool: Reserves ratio changed"
        );

        // Calculate token amounts
        if (supply == 0) { // Initialize at 1 pool token minted per base token supplied
            baseIn = baseAvailable;
            tokensMinted = baseIn;
        } else if (_realFYTokenCached == 0) { // Edge case, no fyToken in the Pool after initialization
            baseIn = baseAvailable;
            tokensMinted = supply * baseIn / _baseCached;
        } else {
            // There is an optional virtual trade before the mint
            uint256 baseToSell;
            if (fyTokenToBuy > 0) {
                baseToSell = _buyFYTokenPreview(
                    fyTokenToBuy.u128(),
                    _baseCached,
                    _fyTokenCached
                ); 
            }

            // We use all the available fyTokens, plus a virtual trade if it happened, surplus is in base tokens
            fyTokenIn = fyTokenBalance - _realFYTokenCached;
            tokensMinted = (supply * (fyTokenToBuy + fyTokenIn)) / (_realFYTokenCached - fyTokenToBuy);
            baseIn = baseToSell + ((_baseCached + baseToSell) * tokensMinted) / supply;
            require(baseAvailable >= baseIn, "Pool: Not enough base token in");
        }

        // Update TWAR
        _update(
            (_baseCached + baseIn).u128(),
            (_fyTokenCached + fyTokenIn + tokensMinted).u128(), // Account for the "virtual" fyToken from the new minted LP tokens
            _baseCached,
            _fyTokenCached
        );

        // Execute mint
        _mint(to, tokensMinted);

        // Return any unused base
        if (baseAvailable - baseIn > 0) base.safeTransfer(remainder, baseAvailable - baseIn);

        emit Liquidity(maturity, msg.sender, to, address(0), -(baseIn.i256()), -(fyTokenIn.i256()), tokensMinted.i256());
    }

    /// @dev Burn liquidity tokens in exchange for base and fyToken.
    /// The liquidity tokens need to be in this contract.
    /// @param baseTo Wallet receiving the base.
    /// @param fyTokenTo Wallet receiving the fyToken.
    /// @param minRatio Minimum ratio of base to fyToken in the pool.
    /// @param maxRatio Maximum ratio of base to fyToken in the pool.
    /// @return The amount of tokens burned and returned (tokensBurned, bases, fyTokens).
    function burn(address baseTo, address fyTokenTo, uint256 minRatio, uint256 maxRatio)
        external override
        returns (uint256, uint256, uint256)
    {
        return _burnInternal(baseTo, fyTokenTo, false, minRatio, maxRatio);
    }

    /// @dev Burn liquidity tokens in exchange for base.
    /// The liquidity provider needs to have called `pool.approve`.
    /// @param to Wallet receiving the base and fyToken.
    /// @param minRatio Minimum ratio of base to fyToken in the pool.
    /// @param maxRatio Minimum ratio of base to fyToken in the pool.
    /// @return tokensBurned The amount of lp tokens burned.
    /// @return baseOut The amount of base tokens returned.
    function burnForBase(address to, uint256 minRatio, uint256 maxRatio)
        external override
        returns (uint256 tokensBurned, uint256 baseOut)
    {
        (tokensBurned, baseOut, ) = _burnInternal(to, address(0), true, minRatio, maxRatio);
    }


    /// @dev Burn liquidity tokens in exchange for base.
    /// The liquidity provider needs to have called `pool.approve`.
    /// @param baseTo Wallet receiving the base.
    /// @param fyTokenTo Wallet receiving the fyToken.
    /// @param tradeToBase Whether the resulting fyToken should be traded for base tokens.
    /// @param minRatio Minimum ratio of base to fyToken in the pool.
    /// @param maxRatio Minimum ratio of base to fyToken in the pool.
    /// @return tokensBurned The amount of pool tokens burned.
    /// @return tokenOut The amount of base tokens returned.
    /// @return fyTokenOut The amount of fyTokens returned.
    function _burnInternal(address baseTo, address fyTokenTo, bool tradeToBase, uint256 minRatio, uint256 maxRatio)
        internal
        returns (uint256 tokensBurned, uint256 tokenOut, uint256 fyTokenOut)
    {
        
        // Gather data
        tokensBurned = _balanceOf[address(this)];
        uint256 supply = _totalSupply;
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        uint256 _realFYTokenCached = _fyTokenCached - supply;    // The fyToken cache includes the virtual fyToken, equal to the supply

        // Check the burn wasn't sandwiched
        require (
            _realFYTokenCached == 0 || (
                uint256(_baseCached) * 1e18 / _realFYTokenCached >= minRatio &&
                uint256(_baseCached) * 1e18 / _realFYTokenCached <= maxRatio
            ),
            "Pool: Reserves ratio changed"
        );

        // Calculate trade
        tokenOut = (tokensBurned * _baseCached) / supply;
        fyTokenOut = (tokensBurned * _realFYTokenCached) / supply;

        if (tradeToBase) {
            tokenOut += YieldMath.baseOutForFYTokenIn(                      // This is a virtual sell
                (_baseCached - tokenOut.u128()) * scaleFactor,              // Cache, minus virtual burn
                (_fyTokenCached - fyTokenOut.u128()) * scaleFactor,         // Cache, minus virtual burn
                fyTokenOut.u128() * scaleFactor,                            // Sell the virtual fyToken obtained
                maturity - uint32(block.timestamp),                         // This can't be called after maturity
                ts,
                g2
            ) / scaleFactor;
            fyTokenOut = 0;
        }

        // Update TWAR
        _update(
            (_baseCached - tokenOut).u128(),
            (_fyTokenCached - fyTokenOut - tokensBurned).u128(),
            _baseCached,
            _fyTokenCached
        );

        // Transfer assets
        _burn(address(this), tokensBurned);
        base.safeTransfer(baseTo, tokenOut);
        if (fyTokenOut > 0) IERC20(address(fyToken)).safeTransfer(fyTokenTo, fyTokenOut);

        emit Liquidity(maturity, msg.sender, baseTo, fyTokenTo, tokenOut.i256(), fyTokenOut.i256(), -(tokensBurned.i256()));
    }

    // ---- Trading ----

    /// @dev Sell base for fyToken.
    /// The trader needs to have transferred the amount of base to sell to the pool before in the same transaction.
    /// @param to Wallet receiving the fyToken being bought
    /// @param min Minimm accepted amount of fyToken
    /// @return Amount of fyToken that will be deposited on `to` wallet
    function sellBase(address to, uint128 min)
        external override
        returns(uint128)
    {
        // Calculate trade
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        uint112 _baseBalance = _getBaseBalance();
        uint112 _fyTokenBalance = _getFYTokenBalance();
        uint128 baseIn = _baseBalance - _baseCached;
        uint128 fyTokenOut = _sellBasePreview(
            baseIn,
            _baseCached,
            _fyTokenBalance
        );

        // Slippage check
        require(
            fyTokenOut >= min,
            "Pool: Not enough fyToken obtained"
        );

        // Update TWAR
        _update(
            _baseBalance,
            _fyTokenBalance - fyTokenOut,
            _baseCached,
            _fyTokenCached
        );

        // Transfer assets
        IERC20(address(fyToken)).safeTransfer(to, fyTokenOut);

        emit Trade(maturity, msg.sender, to, -(baseIn.i128()), fyTokenOut.i128());
        return fyTokenOut;
    }

    /// @dev Returns how much fyToken would be obtained by selling `baseIn` base
    /// @param baseIn Amount of base hypothetically sold.
    /// @return Amount of fyToken hypothetically bought.
    function sellBasePreview(uint128 baseIn)
        external view override
        returns(uint128)
    {
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        return _sellBasePreview(baseIn, _baseCached, _fyTokenCached);
    }

    /// @dev Returns how much fyToken would be obtained by selling `baseIn` base
    function _sellBasePreview(
        uint128 baseIn,
        uint112 baseBalance,
        uint112 fyTokenBalance
    )
        private view
        beforeMaturity
        returns(uint128)
    {
        uint128 fyTokenOut = YieldMath.fyTokenOutForBaseIn(
            baseBalance * scaleFactor,
            fyTokenBalance * scaleFactor,
            baseIn * scaleFactor,
            maturity - uint32(block.timestamp),             // This can't be called after maturity
            ts,
            g1
        ) / scaleFactor;

        require(
            fyTokenBalance - fyTokenOut >= baseBalance + baseIn,
            "Pool: fyToken balance too low"
        );

        return fyTokenOut;
    }

    /// @dev Buy base for fyToken
    /// The trader needs to have called `fyToken.approve`
    /// @param to Wallet receiving the base being bought
    /// @param tokenOut Amount of base being bought that will be deposited in `to` wallet
    /// @param max Maximum amount of fyToken that will be paid for the trade
    /// @return Amount of fyToken that will be taken from caller
    function buyBase(address to, uint128 tokenOut, uint128 max)
        external override
        returns(uint128)
    {
        // Calculate trade
        uint128 fyTokenBalance = _getFYTokenBalance();
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        uint128 fyTokenIn = _buyBasePreview(
            tokenOut,
            _baseCached,
            _fyTokenCached
        );
        require(
            fyTokenBalance - _fyTokenCached >= fyTokenIn,
            "Pool: Not enough fyToken in"
        );

        // Slippage check
        require(
            fyTokenIn <= max,
            "Pool: Too much fyToken in"
        );

        // Update TWAR
        _update(
            _baseCached - tokenOut,
            _fyTokenCached + fyTokenIn,
            _baseCached,
            _fyTokenCached
        );

        // Transfer assets
        base.safeTransfer(to, tokenOut);

        emit Trade(maturity, msg.sender, to, tokenOut.i128(), -(fyTokenIn.i128()));
        return fyTokenIn;
    }

    /// @dev Returns how much fyToken would be required to buy `tokenOut` base.
    /// @param tokenOut Amount of base hypothetically desired.
    /// @return Amount of fyToken hypothetically required.
    function buyBasePreview(uint128 tokenOut)
        external view override
        returns(uint128)
    {
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        return _buyBasePreview(tokenOut, _baseCached, _fyTokenCached);
    }

    /// @dev Returns how much fyToken would be required to buy `tokenOut` base.
    function _buyBasePreview(
        uint128 tokenOut,
        uint112 baseBalance,
        uint112 fyTokenBalance
    )
        private view
        beforeMaturity
        returns(uint128)
    {
        return YieldMath.fyTokenInForBaseOut(
            baseBalance * scaleFactor,
            fyTokenBalance * scaleFactor,
            tokenOut * scaleFactor,
            maturity - uint32(block.timestamp),             // This can't be called after maturity
            ts,
            g2
        ) / scaleFactor;
    }

    /// @dev Sell fyToken for base
    /// The trader needs to have transferred the amount of fyToken to sell to the pool before in the same transaction.
    /// @param to Wallet receiving the base being bought
    /// @param min Minimm accepted amount of base
    /// @return Amount of base that will be deposited on `to` wallet
    function sellFYToken(address to, uint128 min)
        external override
        returns(uint128)
    {
        // Calculate trade
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        uint112 _fyTokenBalance = _getFYTokenBalance();
        uint112 _baseBalance = _getBaseBalance();
        uint128 fyTokenIn = _fyTokenBalance - _fyTokenCached;
        uint128 baseOut = _sellFYTokenPreview(
            fyTokenIn,
            _baseCached,
            _fyTokenCached
        );

        // Slippage check
        require(
            baseOut >= min,
            "Pool: Not enough base obtained"
        );

        // Update TWAR
        _update(
            _baseBalance - baseOut,
            _fyTokenBalance,
            _baseCached,
            _fyTokenCached
        );

        // Transfer assets
        base.safeTransfer(to, baseOut);

        emit Trade(maturity, msg.sender, to, baseOut.i128(), -(fyTokenIn.i128()));
        return baseOut;
    }

    /// @dev Returns how much base would be obtained by selling `fyTokenIn` fyToken.
    /// @param fyTokenIn Amount of fyToken hypothetically sold.
    /// @return Amount of base hypothetically bought.
    function sellFYTokenPreview(uint128 fyTokenIn)
        external view override
        returns(uint128)
    {
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        return _sellFYTokenPreview(fyTokenIn, _baseCached, _fyTokenCached);
    }

    /// @dev Returns how much base would be obtained by selling `fyTokenIn` fyToken.
    function _sellFYTokenPreview(
        uint128 fyTokenIn,
        uint112 baseBalance,
        uint112 fyTokenBalance
    )
        private view
        beforeMaturity
        returns(uint128)
    {
        return YieldMath.baseOutForFYTokenIn(
            baseBalance * scaleFactor,
            fyTokenBalance * scaleFactor,
            fyTokenIn * scaleFactor,
            maturity - uint32(block.timestamp),             // This can't be called after maturity
            ts,
            g2
        ) / scaleFactor;
    }

    /// @dev Buy fyToken for base
    /// The trader needs to have called `base.approve`
    /// @param to Wallet receiving the fyToken being bought
    /// @param fyTokenOut Amount of fyToken being bought that will be deposited in `to` wallet
    /// @param max Maximum amount of base token that will be paid for the trade
    /// @return Amount of base that will be taken from caller's wallet
    function buyFYToken(address to, uint128 fyTokenOut, uint128 max)
        external override
        returns(uint128)
    {
        // Calculate trade
        uint128 baseBalance = _getBaseBalance();
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        uint128 baseIn = _buyFYTokenPreview(
            fyTokenOut,
            _baseCached,
            _fyTokenCached
        );
        require(
            baseBalance - _baseCached >= baseIn,
            "Pool: Not enough base token in"
        );

        // Slippage check
        require(
            baseIn <= max,
            "Pool: Too much base token in"
        );

        // Update TWAR
        _update(
            _baseCached + baseIn,
            _fyTokenCached - fyTokenOut,
            _baseCached,
            _fyTokenCached
        );

        // Transfer assets
        IERC20(address(fyToken)).safeTransfer(to, fyTokenOut);

        emit Trade(maturity, msg.sender, to, -(baseIn.i128()), fyTokenOut.i128());
        return baseIn;
    }

    /// @dev Returns how much base would be required to buy `fyTokenOut` fyToken.
    /// @param fyTokenOut Amount of fyToken hypothetically desired.
    /// @return Amount of base hypothetically required.
    function buyFYTokenPreview(uint128 fyTokenOut)
        external view override
        returns(uint128)
    {
        (uint112 _baseCached, uint112 _fyTokenCached) =
            (baseCached, fyTokenCached);
        return _buyFYTokenPreview(fyTokenOut, _baseCached, _fyTokenCached);
    }

    /// @dev Returns how much base would be required to buy `fyTokenOut` fyToken.
    function _buyFYTokenPreview(
        uint128 fyTokenOut,
        uint128 baseBalance,
        uint128 fyTokenBalance
    )
        private view
        beforeMaturity
        returns(uint128)
    {
        uint128 baseIn = YieldMath.baseInForFYTokenOut(
            baseBalance * scaleFactor,
            fyTokenBalance * scaleFactor,
            fyTokenOut * scaleFactor,
            maturity - uint32(block.timestamp),             // This can't be called after maturity
            ts,
            g1
        ) / scaleFactor;

        require(
            fyTokenBalance - fyTokenOut >= baseBalance + baseIn,
            "Pool: fyToken balance too low"
        );

        return baseIn;
    }
}

// File: @yield-protocol/utils-v2/contracts/token/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
// File: @yield-protocol/utils-v2/contracts/token/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// Taken from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/extensions/IERC20Metadata.sol

pragma solidity ^0.8.0;

import "./IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}
// File: @yield-protocol/utils-v2/contracts/token/ERC20Permit.sol



// SPDX-License-Identifier: MIT
// Adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/53516bc555a454862470e7860a9b5254db4d00f5/contracts/token/ERC20/ERC20Permit.sol
pragma solidity ^0.8.0;

import "./ERC20.sol";
import "./IERC2612.sol";

/**
 * @dev Extension of {ERC20} that allows token holders to use their tokens
 * without sending any transactions by setting {IERC20-allowance} with a
 * signature using the {permit} method, and then spend them via
 * {IERC20-transferFrom}.
 *
 * The {permit} signature mechanism conforms to the {IERC2612} interface.
 */
abstract contract ERC20Permit is ERC20, IERC2612 {
    mapping (address => uint256) public override nonces;

    bytes32 public immutable PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 private immutable _DOMAIN_SEPARATOR;
    uint256 public immutable deploymentChainId;

    constructor(string memory name_, string memory symbol_, uint8 decimals_) ERC20(name_, symbol_, decimals_) {
        deploymentChainId = block.chainid;
        _DOMAIN_SEPARATOR = _calculateDomainSeparator(block.chainid);
    }

    /// @dev Calculate the DOMAIN_SEPARATOR.
    function _calculateDomainSeparator(uint256 chainId) private view returns (bytes32) {
        return keccak256(
            abi.encode(
                keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
                keccak256(bytes(name)),
                keccak256(bytes(version())),
                chainId,
                address(this)
            )
        );
    }

    /// @dev Return the DOMAIN_SEPARATOR.
    function DOMAIN_SEPARATOR() external view returns (bytes32) {
        return block.chainid == deploymentChainId ? _DOMAIN_SEPARATOR : _calculateDomainSeparator(block.chainid);
    }

    /// @dev Setting the version as a function so that it can be overriden
    function version() public pure virtual returns(string memory) { return "1"; }

    /**
     * @dev See {IERC2612-permit}.
     *
     * In cases where the free option is not a concern, deadline can simply be
     * set to uint(-1), so it should be seen as an optional parameter
     */
    function permit(address owner, address spender, uint256 amount, uint256 deadline, uint8 v, bytes32 r, bytes32 s) external virtual override {
        require(deadline >= block.timestamp, "ERC20Permit: expired deadline");

        bytes32 hashStruct = keccak256(
            abi.encode(
                PERMIT_TYPEHASH,
                owner,
                spender,
                amount,
                nonces[owner]++,
                deadline
            )
        );

        bytes32 hash = keccak256(
            abi.encodePacked(
                "\x19\x01",
                block.chainid == deploymentChainId ? _DOMAIN_SEPARATOR : _calculateDomainSeparator(block.chainid),
                hashStruct
            )
        );

        address signer = ecrecover(hash, v, r, s);
        require(
            signer != address(0) && signer == owner,
            "ERC20Permit: invalid signature"
        );

        _setAllowance(owner, spender, amount);
    }
}

// File: @yield-protocol/utils-v2/contracts/token/MinimalTransferHelper.sol



// SPDX-License-Identifier: MIT
// Taken from https://github.com/Uniswap/uniswap-lib/blob/master/contracts/libraries/TransferHelper.sol

pragma solidity >=0.6.0;

import "./IERC20.sol";
import "../utils/RevertMsgExtractor.sol";


// helper methods for transferring ERC20 tokens that do not consistently return true/false
library MinimalTransferHelper {
    /// @notice Transfers tokens from msg.sender to a recipient
    /// @dev Errors with the underlying revert message if transfer fails
    /// @param token The contract address of the token which will be transferred
    /// @param to The recipient of the transfer
    /// @param value The value of the transfer
    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        (bool success, bytes memory data) = address(token).call(abi.encodeWithSelector(IERC20.transfer.selector, to, value));
        if (!(success && (data.length == 0 || abi.decode(data, (bool))))) revert(RevertMsgExtractor.getRevertMsg(data));
    }
}
// File: @yield-protocol/utils-v2/contracts/cast/CastU256U128.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;


library CastU256U128 {
    /// @dev Safely cast an uint256 to an uint128
    function u128(uint256 x) internal pure returns (uint128 y) {
        require (x <= type(uint128).max, "Cast overflow");
        y = uint128(x);
    }
}
// File: @yield-protocol/utils-v2/contracts/cast/CastU256U112.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;


library CastU256U112 {
    /// @dev Safely cast an uint256 to an uint112
    function u112(uint256 x) internal pure returns (uint112 y) {
        require (x <= type(uint112).max, "Cast overflow");
        y = uint112(x);
    }
}
// File: @yield-protocol/utils-v2/contracts/cast/CastU256I256.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;


library CastU256I256 {
    /// @dev Safely cast an uint256 to an int256
    function i256(uint256 x) internal pure returns (int256 y) {
        require (x <= uint256(type(int256).max), "Cast overflow");
        y = int256(x);
    }
}
// File: @yield-protocol/utils-v2/contracts/cast/CastU128U112.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;


library CastU128U112 {
    /// @dev Safely cast an uint128 to an uint112
    function u112(uint128 x) internal pure returns (uint112 y) {
        require (x <= uint128(type(uint112).max), "Cast overflow");
        y = uint112(x);
    }
}
// File: @yield-protocol/utils-v2/contracts/cast/CastU128I128.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.0;


library CastU128I128 {
    /// @dev Safely cast an uint128 to an int128
    function i128(uint128 x) internal pure returns (int128 y) {
        require (x <= uint128(type(int128).max), "Cast overflow");
        y = int128(x);
    }
}
// File: @yield-protocol/yieldspace-interfaces/IPool.sol



// SPDX-License-Identifier: MIT
pragma solidity >= 0.8.0;
import "@yield-protocol/utils-v2/contracts/token/IERC20.sol";
import "@yield-protocol/utils-v2/contracts/token/IERC2612.sol";
import "@yield-protocol/vault-interfaces/IFYToken.sol";


interface IPool is IERC20, IERC2612 {
    function ts() external view returns(int128);
    function g1() external view returns(int128);
    function g2() external view returns(int128);
    function maturity() external view returns(uint32);
    function scaleFactor() external view returns(uint96);
    function getCache() external view returns (uint112, uint112, uint32);
    function base() external view returns(IERC20);
    function fyToken() external view returns(IFYToken);
    function getBaseBalance() external view returns(uint112);
    function getFYTokenBalance() external view returns(uint112);
    function retrieveBase(address to) external returns(uint128 retrieved);
    function retrieveFYToken(address to) external returns(uint128 retrieved);
    function sellBase(address to, uint128 min) external returns(uint128);
    function buyBase(address to, uint128 baseOut, uint128 max) external returns(uint128);
    function sellFYToken(address to, uint128 min) external returns(uint128);
    function buyFYToken(address to, uint128 fyTokenOut, uint128 max) external returns(uint128);
    function sellBasePreview(uint128 baseIn) external view returns(uint128);
    function buyBasePreview(uint128 baseOut) external view returns(uint128);
    function sellFYTokenPreview(uint128 fyTokenIn) external view returns(uint128);
    function buyFYTokenPreview(uint128 fyTokenOut) external view returns(uint128);
    function mint(address to, address remainder, uint256 minRatio, uint256 maxRatio) external returns (uint256, uint256, uint256);
    function mintWithBase(address to, address remainder, uint256 fyTokenToBuy, uint256 minRatio, uint256 maxRatio) external returns (uint256, uint256, uint256);
    function burn(address baseTo, address fyTokenTo, uint256 minRatio, uint256 maxRatio) external returns (uint256, uint256, uint256);
    function burnForBase(address to, uint256 minRatio, uint256 maxRatio) external returns (uint256, uint256);
}
// File: @yield-protocol/vault-interfaces/IFYToken.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@yield-protocol/utils-v2/contracts/token/IERC20.sol";

interface IFYToken is IERC20 {
    /// @dev Asset that is returned on redemption.
    function underlying() external view returns (address);

    /// @dev Unix time at which redemption of fyToken for underlying are possible
    function maturity() external view returns (uint256);

    /// @dev Record price data at maturity
    function mature() external;

    /// @dev Mint fyToken providing an equal amount of underlying to the protocol
    function mintWithUnderlying(address to, uint256 amount) external;

    /// @dev Burn fyToken after maturity for an amount of underlying.
    function redeem(address to, uint256 amount) external returns (uint256);

    /// @dev Mint fyToken.
    /// This function can only be called by other Yield contracts, not users directly.
    /// @param to Wallet to mint the fyToken in.
    /// @param fyTokenAmount Amount of fyToken to mint.
    function mint(address to, uint256 fyTokenAmount) external;

    /// @dev Burn fyToken.
    /// This function can only be called by other Yield contracts, not users directly.
    /// @param from Wallet to burn the fyToken from.
    /// @param fyTokenAmount Amount of fyToken to burn.
    function burn(address from, uint256 fyTokenAmount) external;
}

// File: @yield-protocol/yieldspace-v2/contracts/YieldMath.sol



// SPDX-License-Identifier: BUSL-1.1
pragma solidity 0.8.6;

import "./Math64x64.sol";

library Exp64x64 {
  /**
   * Raise given number x into power specified as a simple fraction y/z and then
   * multiply the result by the normalization factor 2^(128 * (1 - y/z)).
   * Revert if z is zero, or if both x and y are zeros.
   *
   * @param x number to raise into given power y/z
   * @param y numerator of the power to raise x into
   * @param z denominator of the power to raise x into
   * @return x raised into power y/z and then multiplied by 2^(128 * (1 - y/z))
   */
  function pow(uint128 x, uint128 y, uint128 z)
  internal pure returns(uint128) {
    unchecked {
      require(z != 0);

      if(x == 0) {
        require(y != 0);
        return 0;
      } else {
        uint256 l =
          uint256(0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF - log_2(x)) * y / z;
        if(l > 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF) return 0;
        else return pow_2(uint128(0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF - l));
      }
    }
  }

  /**
   * Calculate base 2 logarithm of an unsigned 128-bit integer number.  Revert
   * in case x is zero.
   *
   * @param x number to calculate base 2 logarithm of
   * @return base 2 logarithm of x, multiplied by 2^121
   */
  function log_2(uint128 x)
  internal pure returns(uint128) {
    unchecked {
      require(x != 0);

      uint b = x;

      uint l = 0xFE000000000000000000000000000000;

      if(b < 0x10000000000000000) {l -= 0x80000000000000000000000000000000; b <<= 64;}
      if(b < 0x1000000000000000000000000) {l -= 0x40000000000000000000000000000000; b <<= 32;}
      if(b < 0x10000000000000000000000000000) {l -= 0x20000000000000000000000000000000; b <<= 16;}
      if(b < 0x1000000000000000000000000000000) {l -= 0x10000000000000000000000000000000; b <<= 8;}
      if(b < 0x10000000000000000000000000000000) {l -= 0x8000000000000000000000000000000; b <<= 4;}
      if(b < 0x40000000000000000000000000000000) {l -= 0x4000000000000000000000000000000; b <<= 2;}
      if(b < 0x80000000000000000000000000000000) {l -= 0x2000000000000000000000000000000; b <<= 1;}

      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000000000000000;} /*
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x1000;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x800;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x400;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x200;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x100;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x80;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x40;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x20;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x10;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x8;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x4;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) {b >>= 1; l |= 0x2;}
      b = b * b >> 127; if(b >= 0x100000000000000000000000000000000) l |= 0x1; */

      return uint128(l);
    }
  }

  /**
   * Calculate 2 raised into given power.
   *
   * @param x power to raise 2 into, multiplied by 2^121
   * @return 2 raised into given power
   */
  function pow_2(uint128 x)
  internal pure returns(uint128) {
    unchecked {
      uint r = 0x80000000000000000000000000000000;
      if(x & 0x1000000000000000000000000000000 > 0) r = r * 0xb504f333f9de6484597d89b3754abe9f >> 127;
      if(x & 0x800000000000000000000000000000 > 0) r = r * 0x9837f0518db8a96f46ad23182e42f6f6 >> 127;
      if(x & 0x400000000000000000000000000000 > 0) r = r * 0x8b95c1e3ea8bd6e6fbe4628758a53c90 >> 127;
      if(x & 0x200000000000000000000000000000 > 0) r = r * 0x85aac367cc487b14c5c95b8c2154c1b2 >> 127;
      if(x & 0x100000000000000000000000000000 > 0) r = r * 0x82cd8698ac2ba1d73e2a475b46520bff >> 127;
      if(x & 0x80000000000000000000000000000 > 0) r = r * 0x8164d1f3bc0307737be56527bd14def4 >> 127;
      if(x & 0x40000000000000000000000000000 > 0) r = r * 0x80b1ed4fd999ab6c25335719b6e6fd20 >> 127;
      if(x & 0x20000000000000000000000000000 > 0) r = r * 0x8058d7d2d5e5f6b094d589f608ee4aa2 >> 127;
      if(x & 0x10000000000000000000000000000 > 0) r = r * 0x802c6436d0e04f50ff8ce94a6797b3ce >> 127;
      if(x & 0x8000000000000000000000000000 > 0) r = r * 0x8016302f174676283690dfe44d11d008 >> 127;
      if(x & 0x4000000000000000000000000000 > 0) r = r * 0x800b179c82028fd0945e54e2ae18f2f0 >> 127;
      if(x & 0x2000000000000000000000000000 > 0) r = r * 0x80058baf7fee3b5d1c718b38e549cb93 >> 127;
      if(x & 0x1000000000000000000000000000 > 0) r = r * 0x8002c5d00fdcfcb6b6566a58c048be1f >> 127;
      if(x & 0x800000000000000000000000000 > 0) r = r * 0x800162e61bed4a48e84c2e1a463473d9 >> 127;
      if(x & 0x400000000000000000000000000 > 0) r = r * 0x8000b17292f702a3aa22beacca949013 >> 127;
      if(x & 0x200000000000000000000000000 > 0) r = r * 0x800058b92abbae02030c5fa5256f41fe >> 127;
      if(x & 0x100000000000000000000000000 > 0) r = r * 0x80002c5c8dade4d71776c0f4dbea67d6 >> 127;
      if(x & 0x80000000000000000000000000 > 0) r = r * 0x8000162e44eaf636526be456600bdbe4 >> 127;
      if(x & 0x40000000000000000000000000 > 0) r = r * 0x80000b1721fa7c188307016c1cd4e8b6 >> 127;
      if(x & 0x20000000000000000000000000 > 0) r = r * 0x8000058b90de7e4cecfc487503488bb1 >> 127;
      if(x & 0x10000000000000000000000000 > 0) r = r * 0x800002c5c8678f36cbfce50a6de60b14 >> 127;
      if(x & 0x8000000000000000000000000 > 0) r = r * 0x80000162e431db9f80b2347b5d62e516 >> 127;
      if(x & 0x4000000000000000000000000 > 0) r = r * 0x800000b1721872d0c7b08cf1e0114152 >> 127;
      if(x & 0x2000000000000000000000000 > 0) r = r * 0x80000058b90c1aa8a5c3736cb77e8dff >> 127;
      if(x & 0x1000000000000000000000000 > 0) r = r * 0x8000002c5c8605a4635f2efc2362d978 >> 127;
      if(x & 0x800000000000000000000000 > 0) r = r * 0x800000162e4300e635cf4a109e3939bd >> 127;
      if(x & 0x400000000000000000000000 > 0) r = r * 0x8000000b17217ff81bef9c551590cf83 >> 127;
      if(x & 0x200000000000000000000000 > 0) r = r * 0x800000058b90bfdd4e39cd52c0cfa27c >> 127;
      if(x & 0x100000000000000000000000 > 0) r = r * 0x80000002c5c85fe6f72d669e0e76e411 >> 127;
      if(x & 0x80000000000000000000000 > 0) r = r * 0x8000000162e42ff18f9ad35186d0df28 >> 127;
      if(x & 0x40000000000000000000000 > 0) r = r * 0x80000000b17217f84cce71aa0dcfffe7 >> 127;
      if(x & 0x20000000000000000000000 > 0) r = r * 0x8000000058b90bfc07a77ad56ed22aaa >> 127;
      if(x & 0x10000000000000000000000 > 0) r = r * 0x800000002c5c85fdfc23cdead40da8d6 >> 127;
      if(x & 0x8000000000000000000000 > 0) r = r * 0x80000000162e42fefc25eb1571853a66 >> 127;
      if(x & 0x4000000000000000000000 > 0) r = r * 0x800000000b17217f7d97f692baacded5 >> 127;
      if(x & 0x2000000000000000000000 > 0) r = r * 0x80000000058b90bfbead3b8b5dd254d7 >> 127;
      if(x & 0x1000000000000000000000 > 0) r = r * 0x8000000002c5c85fdf4eedd62f084e67 >> 127;
      if(x & 0x800000000000000000000 > 0) r = r * 0x800000000162e42fefa58aef378bf586 >> 127;
      if(x & 0x400000000000000000000 > 0) r = r * 0x8000000000b17217f7d24a78a3c7ef02 >> 127;
      if(x & 0x200000000000000000000 > 0) r = r * 0x800000000058b90bfbe9067c93e474a6 >> 127;
      if(x & 0x100000000000000000000 > 0) r = r * 0x80000000002c5c85fdf47b8e5a72599f >> 127;
      if(x & 0x80000000000000000000 > 0) r = r * 0x8000000000162e42fefa3bdb315934a2 >> 127;
      if(x & 0x40000000000000000000 > 0) r = r * 0x80000000000b17217f7d1d7299b49c46 >> 127;
      if(x & 0x20000000000000000000 > 0) r = r * 0x8000000000058b90bfbe8e9a8d1c4ea0 >> 127;
      if(x & 0x10000000000000000000 > 0) r = r * 0x800000000002c5c85fdf4745969ea76f >> 127;
      if(x & 0x8000000000000000000 > 0) r = r * 0x80000000000162e42fefa3a0df5373bf >> 127;
      if(x & 0x4000000000000000000 > 0) r = r * 0x800000000000b17217f7d1cff4aac1e1 >> 127;
      if(x & 0x2000000000000000000 > 0) r = r * 0x80000000000058b90bfbe8e7db95a2f1 >> 127;
      if(x & 0x1000000000000000000 > 0) r = r * 0x8000000000002c5c85fdf473e61ae1f8 >> 127;
      if(x & 0x800000000000000000 > 0) r = r * 0x800000000000162e42fefa39f121751c >> 127;
      if(x & 0x400000000000000000 > 0) r = r * 0x8000000000000b17217f7d1cf815bb96 >> 127;
      if(x & 0x200000000000000000 > 0) r = r * 0x800000000000058b90bfbe8e7bec1e0d >> 127;
      if(x & 0x100000000000000000 > 0) r = r * 0x80000000000002c5c85fdf473dee5f17 >> 127;
      if(x & 0x80000000000000000 > 0) r = r * 0x8000000000000162e42fefa39ef5438f >> 127;
      if(x & 0x40000000000000000 > 0) r = r * 0x80000000000000b17217f7d1cf7a26c8 >> 127;
      if(x & 0x20000000000000000 > 0) r = r * 0x8000000000000058b90bfbe8e7bcf4a4 >> 127;
      if(x & 0x10000000000000000 > 0) r = r * 0x800000000000002c5c85fdf473de72a2 >> 127; /*
      if(x & 0x8000000000000000 > 0) r = r * 0x80000000000000162e42fefa39ef3765 >> 127;
      if(x & 0x4000000000000000 > 0) r = r * 0x800000000000000b17217f7d1cf79b37 >> 127;
      if(x & 0x2000000000000000 > 0) r = r * 0x80000000000000058b90bfbe8e7bcd7d >> 127;
      if(x & 0x1000000000000000 > 0) r = r * 0x8000000000000002c5c85fdf473de6b6 >> 127;
      if(x & 0x800000000000000 > 0) r = r * 0x800000000000000162e42fefa39ef359 >> 127;
      if(x & 0x400000000000000 > 0) r = r * 0x8000000000000000b17217f7d1cf79ac >> 127;
      if(x & 0x200000000000000 > 0) r = r * 0x800000000000000058b90bfbe8e7bcd6 >> 127;
      if(x & 0x100000000000000 > 0) r = r * 0x80000000000000002c5c85fdf473de6a >> 127;
      if(x & 0x80000000000000 > 0) r = r * 0x8000000000000000162e42fefa39ef35 >> 127;
      if(x & 0x40000000000000 > 0) r = r * 0x80000000000000000b17217f7d1cf79a >> 127;
      if(x & 0x20000000000000 > 0) r = r * 0x8000000000000000058b90bfbe8e7bcd >> 127;
      if(x & 0x10000000000000 > 0) r = r * 0x800000000000000002c5c85fdf473de6 >> 127;
      if(x & 0x8000000000000 > 0) r = r * 0x80000000000000000162e42fefa39ef3 >> 127;
      if(x & 0x4000000000000 > 0) r = r * 0x800000000000000000b17217f7d1cf79 >> 127;
      if(x & 0x2000000000000 > 0) r = r * 0x80000000000000000058b90bfbe8e7bc >> 127;
      if(x & 0x1000000000000 > 0) r = r * 0x8000000000000000002c5c85fdf473de >> 127;
      if(x & 0x800000000000 > 0) r = r * 0x800000000000000000162e42fefa39ef >> 127;
      if(x & 0x400000000000 > 0) r = r * 0x8000000000000000000b17217f7d1cf7 >> 127;
      if(x & 0x200000000000 > 0) r = r * 0x800000000000000000058b90bfbe8e7b >> 127;
      if(x & 0x100000000000 > 0) r = r * 0x80000000000000000002c5c85fdf473d >> 127;
      if(x & 0x80000000000 > 0) r = r * 0x8000000000000000000162e42fefa39e >> 127;
      if(x & 0x40000000000 > 0) r = r * 0x80000000000000000000b17217f7d1cf >> 127;
      if(x & 0x20000000000 > 0) r = r * 0x8000000000000000000058b90bfbe8e7 >> 127;
      if(x & 0x10000000000 > 0) r = r * 0x800000000000000000002c5c85fdf473 >> 127;
      if(x & 0x8000000000 > 0) r = r * 0x80000000000000000000162e42fefa39 >> 127;
      if(x & 0x4000000000 > 0) r = r * 0x800000000000000000000b17217f7d1c >> 127;
      if(x & 0x2000000000 > 0) r = r * 0x80000000000000000000058b90bfbe8e >> 127;
      if(x & 0x1000000000 > 0) r = r * 0x8000000000000000000002c5c85fdf47 >> 127;
      if(x & 0x800000000 > 0) r = r * 0x800000000000000000000162e42fefa3 >> 127;
      if(x & 0x400000000 > 0) r = r * 0x8000000000000000000000b17217f7d1 >> 127;
      if(x & 0x200000000 > 0) r = r * 0x800000000000000000000058b90bfbe8 >> 127;
      if(x & 0x100000000 > 0) r = r * 0x80000000000000000000002c5c85fdf4 >> 127;
      if(x & 0x80000000 > 0) r = r * 0x8000000000000000000000162e42fefa >> 127;
      if(x & 0x40000000 > 0) r = r * 0x80000000000000000000000b17217f7d >> 127;
      if(x & 0x20000000 > 0) r = r * 0x8000000000000000000000058b90bfbe >> 127;
      if(x & 0x10000000 > 0) r = r * 0x800000000000000000000002c5c85fdf >> 127;
      if(x & 0x8000000 > 0) r = r * 0x80000000000000000000000162e42fef >> 127;
      if(x & 0x4000000 > 0) r = r * 0x800000000000000000000000b17217f7 >> 127;
      if(x & 0x2000000 > 0) r = r * 0x80000000000000000000000058b90bfb >> 127;
      if(x & 0x1000000 > 0) r = r * 0x8000000000000000000000002c5c85fd >> 127;
      if(x & 0x800000 > 0) r = r * 0x800000000000000000000000162e42fe >> 127;
      if(x & 0x400000 > 0) r = r * 0x8000000000000000000000000b17217f >> 127;
      if(x & 0x200000 > 0) r = r * 0x800000000000000000000000058b90bf >> 127;
      if(x & 0x100000 > 0) r = r * 0x80000000000000000000000002c5c85f >> 127;
      if(x & 0x80000 > 0) r = r * 0x8000000000000000000000000162e42f >> 127;
      if(x & 0x40000 > 0) r = r * 0x80000000000000000000000000b17217 >> 127;
      if(x & 0x20000 > 0) r = r * 0x8000000000000000000000000058b90b >> 127;
      if(x & 0x10000 > 0) r = r * 0x800000000000000000000000002c5c85 >> 127;
      if(x & 0x8000 > 0) r = r * 0x80000000000000000000000000162e42 >> 127;
      if(x & 0x4000 > 0) r = r * 0x800000000000000000000000000b1721 >> 127;
      if(x & 0x2000 > 0) r = r * 0x80000000000000000000000000058b90 >> 127;
      if(x & 0x1000 > 0) r = r * 0x8000000000000000000000000002c5c8 >> 127;
      if(x & 0x800 > 0) r = r * 0x800000000000000000000000000162e4 >> 127;
      if(x & 0x400 > 0) r = r * 0x8000000000000000000000000000b172 >> 127;
      if(x & 0x200 > 0) r = r * 0x800000000000000000000000000058b9 >> 127;
      if(x & 0x100 > 0) r = r * 0x80000000000000000000000000002c5c >> 127;
      if(x & 0x80 > 0) r = r * 0x8000000000000000000000000000162e >> 127;
      if(x & 0x40 > 0) r = r * 0x80000000000000000000000000000b17 >> 127;
      if(x & 0x20 > 0) r = r * 0x8000000000000000000000000000058b >> 127;
      if(x & 0x10 > 0) r = r * 0x800000000000000000000000000002c5 >> 127;
      if(x & 0x8 > 0) r = r * 0x80000000000000000000000000000162 >> 127;
      if(x & 0x4 > 0) r = r * 0x800000000000000000000000000000b1 >> 127;
      if(x & 0x2 > 0) r = r * 0x80000000000000000000000000000058 >> 127;
      if(x & 0x1 > 0) r = r * 0x8000000000000000000000000000002c >> 127; */

      r >>= 127 -(x >> 121);

      return uint128(r);
    }
  }
}

/**
 * Ethereum smart contract library implementing Yield Math model.
 */
library YieldMath {
  using Math64x64 for int128;
  using Math64x64 for uint128;
  using Math64x64 for int256;
  using Math64x64 for uint256;
  using Exp64x64 for uint128;

  uint128 public constant ONE = 0x10000000000000000; // In 64.64
  uint128 public constant TWO = 0x20000000000000000; // In 64.64
  uint256 public constant MAX = type(uint128).max;   // Used for overflow checks
  uint256 public constant VAR = 1e12;                // The logarithm math used is not precise to the wei, but can deviate up to 1e12 from the real value.

  /**
   * Calculate a YieldSpace pool invariant according to the whitepaper
   */
  function invariant(uint128 baseReserves, uint128 fyTokenReserves, uint256 totalSupply, uint128 timeTillMaturity, int128 ts)
      public pure returns(uint128)
  {
    if (totalSupply == 0) return 0;

    unchecked {
      // a = (1 - ts * timeTillMaturity)
      int128 a = int128(ONE).sub(ts.mul(timeTillMaturity.fromUInt()));
      require (a > 0, "YieldMath: Too far from maturity");

      uint256 sum =
      uint256(baseReserves.pow(uint128 (a), ONE)) +
      uint256(fyTokenReserves.pow(uint128 (a), ONE)) >> 1;
      require(sum < MAX, "YieldMath: Sum overflow");

      // We multiply the dividend by 1e18 to get a fixed point number with 18 decimals
      uint256 result = uint256(uint128(sum).pow(ONE, uint128(a))) * 1e18 / totalSupply;
      require (result < MAX, "YieldMath: Result overflow");

      return uint128(result);
    }
  }

  /**
   * Calculate the amount of fyToken a user would get for given amount of Base.
   * https://www.desmos.com/calculator/5nf2xuy6yb
   * @param baseReserves base reserves amount
   * @param fyTokenReserves fyToken reserves amount
   * @param baseAmount base amount to be traded
   * @param timeTillMaturity time till maturity in seconds
   * @param ts time till maturity coefficient, multiplied by 2^64
   * @param g fee coefficient, multiplied by 2^64
   * @return the amount of fyToken a user would get for given amount of Base
   */
  function fyTokenOutForBaseIn(
    uint128 baseReserves, uint128 fyTokenReserves, uint128 baseAmount,
    uint128 timeTillMaturity, int128 ts, int128 g)
  public pure returns(uint128) {
    unchecked {
      uint128 a = _computeA(timeTillMaturity, ts, g);

      // za = baseReserves ** a
      uint256 za = baseReserves.pow(a, ONE);

      // ya = fyTokenReserves ** a
      uint256 ya = fyTokenReserves.pow(a, ONE);

      // zx = baseReserves + baseAmount
      uint256 zx = uint256(baseReserves) + uint256(baseAmount);
      require(zx <= MAX, "YieldMath: Too much base in");

      // zxa = zx ** a
      uint256 zxa = uint128(zx).pow(a, ONE);

      // sum = za + ya - zxa
      uint256 sum = za + ya - zxa; // z < MAX, y < MAX, a < 1. It can only underflow, not overflow.
      require(sum <= MAX, "YieldMath: Insufficient fyToken reserves");

      // result = fyTokenReserves - (sum ** (1/a))
      uint256 result = uint256(fyTokenReserves) - uint256(uint128(sum).pow(ONE, a));
      require(result <= MAX, "YieldMath: Rounding induced error");

      result = result > VAR ? result - VAR : 0; // Subtract error guard, flooring the result at zero

      return uint128(result);
    }
  }

  /**
   * Calculate the amount of base a user would get for certain amount of fyToken.
   * https://www.desmos.com/calculator/6jlrre7ybt
   * @param baseReserves base reserves amount
   * @param fyTokenReserves fyToken reserves amount
   * @param fyTokenAmount fyToken amount to be traded
   * @param timeTillMaturity time till maturity in seconds
   * @param ts time till maturity coefficient, multiplied by 2^64
   * @param g fee coefficient, multiplied by 2^64
   * @return the amount of Base a user would get for given amount of fyToken
   */
  function baseOutForFYTokenIn(
    uint128 baseReserves, uint128 fyTokenReserves, uint128 fyTokenAmount,
    uint128 timeTillMaturity, int128 ts, int128 g)
  public pure returns(uint128) {
    unchecked {
      uint128 a = _computeA(timeTillMaturity, ts, g);

      // za = baseReserves ** a
      uint256 za = baseReserves.pow(a, ONE);

      // ya = fyTokenReserves ** a
      uint256 ya = fyTokenReserves.pow(a, ONE);

      // yx = fyDayReserves + fyTokenAmount
      uint256 yx = uint256(fyTokenReserves) + uint256(fyTokenAmount);
      require(yx <= MAX, "YieldMath: Too much fyToken in");

      // yxa = yx ** a
      uint256 yxa = uint128(yx).pow(a, ONE);

      // sum = za + ya - yxa
      uint256 sum = za + ya - yxa; // z < MAX, y < MAX, a < 1. It can only underflow, not overflow.
      require(sum <= MAX, "YieldMath: Insufficient base reserves");

      // result = baseReserves - (sum ** (1/a))
      uint256 result = uint256(baseReserves) - uint256(uint128(sum).pow(ONE, a));
      require(result <= MAX, "YieldMath: Rounding induced error");

      result = result > VAR ? result - VAR : 0; // Subtract error guard, flooring the result at zero

      return uint128(result);
    }
  }

  /**
   * Calculate the amount of fyToken a user could sell for given amount of Base.
   * https://www.desmos.com/calculator/0rgnmtckvy
   * @param baseReserves base reserves amount
   * @param fyTokenReserves fyToken reserves amount
   * @param baseAmount Base amount to be traded
   * @param timeTillMaturity time till maturity in seconds
   * @param ts time till maturity coefficient, multiplied by 2^64
   * @param g fee coefficient, multiplied by 2^64
   * @return the amount of fyToken a user could sell for given amount of Base
   */
  function fyTokenInForBaseOut(
    uint128 baseReserves, uint128 fyTokenReserves, uint128 baseAmount,
    uint128 timeTillMaturity, int128 ts, int128 g)
  public pure returns(uint128) {
    unchecked {
      uint128 a = _computeA(timeTillMaturity, ts, g);

      // za = baseReserves ** a
      uint256 za = baseReserves.pow(a, ONE);

      // ya = fyTokenReserves ** a
      uint256 ya = fyTokenReserves.pow(a, ONE);

      // zx = baseReserves - baseAmount
      uint256 zx = uint256(baseReserves) - uint256(baseAmount);
      require(zx <= MAX, "YieldMath: Too much base out");

      // zxa = zx ** a
      uint256 zxa = uint128(zx).pow(a, ONE);

      // sum = za + ya - zxa
      uint256 sum = za + ya - zxa; // z < MAX, y < MAX, a < 1. It can only underflow, not overflow.
      require(sum <= MAX, "YieldMath: Resulting fyToken reserves too high");

      // result = (sum ** (1/a)) - fyTokenReserves
      uint256 result = uint256(uint128(sum).pow(ONE, a)) - uint256(fyTokenReserves);
      require(result <= MAX, "YieldMath: Rounding induced error");

      result = result < MAX - VAR ? result + VAR : MAX; // Add error guard, ceiling the result at max

      return uint128(result);
    }
  }

  /**
   * Calculate the amount of base a user would have to pay for certain amount of fyToken.
   * https://www.desmos.com/calculator/ws5oqj8x5i
   * @param baseReserves Base reserves amount
   * @param fyTokenReserves fyToken reserves amount
   * @param fyTokenAmount fyToken amount to be traded
   * @param timeTillMaturity time till maturity in seconds
   * @param ts time till maturity coefficient, multiplied by 2^64
   * @param g fee coefficient, multiplied by 2^64
   * @return the amount of base a user would have to pay for given amount of
   *         fyToken
   */
  function baseInForFYTokenOut(
    uint128 baseReserves, uint128 fyTokenReserves, uint128 fyTokenAmount,
    uint128 timeTillMaturity, int128 ts, int128 g)
  public pure returns(uint128) {
    unchecked {
      uint128 a = _computeA(timeTillMaturity, ts, g);

      // za = baseReserves ** a
      uint256 za = baseReserves.pow(a, ONE);

      // ya = fyTokenReserves ** a
      uint256 ya = fyTokenReserves.pow(a, ONE);

      // yx = baseReserves - baseAmount
      uint256 yx = uint256(fyTokenReserves) - uint256(fyTokenAmount);
      require(yx <= MAX, "YieldMath: Too much fyToken out");

      // yxa = yx ** a
      uint256 yxa = uint128(yx).pow(a, ONE);

      // sum = za + ya - yxa
      uint256 sum = za + ya - yxa; // z < MAX, y < MAX, a < 1. It can only underflow, not overflow.
      require(sum <= MAX, "YieldMath: Resulting base reserves too high");

      // result = (sum ** (1/a)) - baseReserves
      uint256 result = uint256(uint128(sum).pow(ONE, a)) - uint256(baseReserves);
      require(result <= MAX, "YieldMath: Rounding induced error");

      result = result < MAX - VAR ? result + VAR : MAX; // Add error guard, ceiling the result at max

      return uint128(result);
    }
  }

  /**
   * Calculate the max amount of fyTokens that can be bought from the pool without making the interest rate negative.
   * See section 6.3 of the YieldSpace White paper
   * @param baseReserves Base reserves amount
   * @param fyTokenReserves fyToken reserves amount
   * @param timeTillMaturity time till maturity in seconds
   * @param ts time till maturity coefficient, multiplied by 2^64
   * @param g fee coefficient, multiplied by 2^64
   * @return max amount of fyTokens that can be bought from the pool
   */
  function maxFYTokenOut(
    uint128 baseReserves, uint128 fyTokenReserves,
    uint128 timeTillMaturity, int128 ts, int128 g)
  public pure returns(uint128) {
    if (baseReserves == fyTokenReserves) return 0;
    unchecked {
      uint128 a = _computeA(timeTillMaturity, ts, g);

      // xa = baseReserves ** a
      uint128 xa = baseReserves.pow(a, ONE);

      // ya = fyTokenReserves ** a
      uint128 ya = fyTokenReserves.pow(a, ONE);

      int128 xy2 = (xa + ya).divu(TWO);

      uint inaccessible = uint256(uint128(xy2).pow(ONE, a));
      require(inaccessible <= MAX, "YieldMath: Rounding induced error");

      inaccessible = inaccessible < MAX - VAR ? inaccessible + VAR : MAX; // Add error guard, ceiling the result at max

      return uint128(inaccessible) > fyTokenReserves ? 0 : fyTokenReserves - uint128(inaccessible);
    }
  }

  /**
   * Calculate the max amount of fyTokens that can be sold to into the pool.
   * @param baseReserves Base reserves amount
   * @param fyTokenReserves fyToken reserves amount
   * @param timeTillMaturity time till maturity in seconds
   * @param ts time till maturity coefficient, multiplied by 2^64
   * @param g fee coefficient, multiplied by 2^64
   * @return max amount of fyTokens that can be sold to into the pool
   */
  function maxFYTokenIn(
    uint128 baseReserves, uint128 fyTokenReserves,
    uint128 timeTillMaturity, int128 ts, int128 g)
  public pure returns(uint128) {
    unchecked {
      uint128 b = _computeB(timeTillMaturity, ts, g);

      // xa = baseReserves ** a
      uint128 xa = baseReserves.pow(b, ONE);

      // ya = fyTokenReserves ** a
      uint128 ya = fyTokenReserves.pow(b, ONE);

      uint result = (xa + ya).pow(ONE, b) - fyTokenReserves;
      require(result <= MAX, "YieldMath: Rounding induced error");

      result = result > VAR ? result - VAR : 0; // Subtract error guard, flooring the result at zero

      return uint128(result);
    }
  }

  /**
   * Calculate the max amount of base that can be sold to into the pool without making the interest rate negative.
   * @param baseReserves Base reserves amount
   * @param fyTokenReserves fyToken reserves amount
   * @param timeTillMaturity time till maturity in seconds
   * @param ts time till maturity coefficient, multiplied by 2^64
   * @param g fee coefficient, multiplied by 2^64
   * @return max amount of base that can be sold to into the pool
   */
  function maxBaseIn(
    uint128 baseReserves, uint128 fyTokenReserves,
    uint128 timeTillMaturity, int128 ts, int128 g)
  public pure returns (uint128) {
    uint128 _maxFYTokenOut = maxFYTokenOut(baseReserves, fyTokenReserves, timeTillMaturity, ts, g);
    if (_maxFYTokenOut > 0)
      return baseInForFYTokenOut(baseReserves, fyTokenReserves, _maxFYTokenOut, timeTillMaturity, ts, g);
    return 0;
  }

  /**
   * Calculate the max amount of base that can be bought from the pool.
   * @param baseReserves Base reserves amount
   * @param fyTokenReserves fyToken reserves amount
   * @param timeTillMaturity time till maturity in seconds
   * @param ts time till maturity coefficient, multiplied by 2^64
   * @param g fee coefficient, multiplied by 2^64
   * @return max amount of base that can be bought from the pool
   */
  function maxBaseOut(
    uint128 baseReserves, uint128 fyTokenReserves,
    uint128 timeTillMaturity, int128 ts, int128 g)
  public pure returns (uint128) {
    uint128 _maxFYTokenIn = maxFYTokenIn(baseReserves, fyTokenReserves, timeTillMaturity, ts, g);
    return baseOutForFYTokenIn(baseReserves, fyTokenReserves, _maxFYTokenIn, timeTillMaturity, ts, g);
  }

  function _computeA(uint128 timeTillMaturity, int128 ts, int128 g) private pure returns (uint128) {
    unchecked {
      // t = ts * timeTillMaturity
      int128 t = ts.mul(timeTillMaturity.fromUInt());
      require(t >= 0, "YieldMath: t must be positive"); // Meaning neither T or ts can be negative

      // a = (1 - gt)
      int128 a = int128(ONE).sub(g.mul(t));
      require(a > 0, "YieldMath: Too far from maturity");
      require(a <= int128(ONE), "YieldMath: g must be positive");

      return uint128(a);
    }
  }

  function _computeB(uint128 timeTillMaturity, int128 ts, int128 g) private pure returns (uint128) {
    unchecked {
      // t = ts * timeTillMaturity
      int128 t = ts.mul(timeTillMaturity.fromUInt());
      require(t >= 0, "YieldMath: t must be positive"); // Meaning neither T or ts can be negative

      // b = (1 - t/g)
      int128 b = int128(ONE).sub(t.div(g));
      require(b > 0, "YieldMath: Too far from maturity");
      require(b <= int128(ONE), "YieldMath: g must be positive");

      return uint128(b);
    }
  }
}

// File: @yield-protocol/utils-v2/contracts/token/ERC20.sol



// SPDX-License-Identifier: MIT
// Inspired on token.sol from DappHub. Natspec adpated from OpenZeppelin.

pragma solidity ^0.8.0;
import "./IERC20Metadata.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 * 
 * Calls to {transferFrom} do not check for allowance if the caller is the owner
 * of the funds. This allows to reduce the number of approvals that are necessary.
 *
 * Finally, {transferFrom} does not decrease the allowance if it is set to
 * type(uint256).max. This reduces the gas costs without any likely impact.
 */
contract ERC20 is IERC20Metadata {
    uint256                                           internal  _totalSupply;
    mapping (address => uint256)                      internal  _balanceOf;
    mapping (address => mapping (address => uint256)) internal  _allowance;
    string                                            public override name = "???";
    string                                            public override symbol = "???";
    uint8                                             public override decimals = 18;

    /**
     *  @dev Sets the values for {name}, {symbol} and {decimals}.
     */
    constructor(string memory name_, string memory symbol_, uint8 decimals_) {
        name = name_;
        symbol = symbol_;
        decimals = decimals_;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() external view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address guy) external view virtual override returns (uint256) {
        return _balanceOf[guy];
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) external view virtual override returns (uint256) {
        return _allowance[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     */
    function approve(address spender, uint wad) external virtual override returns (bool) {
        return _setAllowance(msg.sender, spender, wad);
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - the caller must have a balance of at least `wad`.
     */
    function transfer(address dst, uint wad) external virtual override returns (bool) {
        return _transfer(msg.sender, dst, wad);
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `src` must have a balance of at least `wad`.
     * - the caller is not `src`, it must have allowance for ``src``'s tokens of at least
     * `wad`.
     */
    /// if_succeeds {:msg "TransferFrom - decrease allowance"} msg.sender != src ==> old(_allowance[src][msg.sender]) >= wad;
    function transferFrom(address src, address dst, uint wad) external virtual override returns (bool) {
        _decreaseAllowance(src, wad);

        return _transfer(src, dst, wad);
    }

    /**
     * @dev Moves tokens `wad` from `src` to `dst`.
     * 
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `src` must have a balance of at least `amount`.
     */
    /// if_succeeds {:msg "Transfer - src decrease"} old(_balanceOf[src]) >= _balanceOf[src];
    /// if_succeeds {:msg "Transfer - dst increase"} _balanceOf[dst] >= old(_balanceOf[dst]);
    /// if_succeeds {:msg "Transfer - supply"} old(_balanceOf[src]) + old(_balanceOf[dst]) == _balanceOf[src] + _balanceOf[dst];
    function _transfer(address src, address dst, uint wad) internal virtual returns (bool) {
        require(_balanceOf[src] >= wad, "ERC20: Insufficient balance");
        unchecked { _balanceOf[src] = _balanceOf[src] - wad; }
        _balanceOf[dst] = _balanceOf[dst] + wad;

        emit Transfer(src, dst, wad);

        return true;
    }

    /**
     * @dev Sets the allowance granted to `spender` by `owner`.
     *
     * Emits an {Approval} event indicating the updated allowance.
     */
    function _setAllowance(address owner, address spender, uint wad) internal virtual returns (bool) {
        _allowance[owner][spender] = wad;
        emit Approval(owner, spender, wad);

        return true;
    }

    /**
     * @dev Decreases the allowance granted to the caller by `src`, unless src == msg.sender or _allowance[src][msg.sender] == MAX
     *
     * Emits an {Approval} event indicating the updated allowance, if the allowance is updated.
     *
     * Requirements:
     *
     * - `spender` must have allowance for the caller of at least
     * `wad`, unless src == msg.sender
     */
    /// if_succeeds {:msg "Decrease allowance - underflow"} old(_allowance[src][msg.sender]) <= _allowance[src][msg.sender];
    function _decreaseAllowance(address src, uint wad) internal virtual returns (bool) {
        if (src != msg.sender) {
            uint256 allowed = _allowance[src][msg.sender];
            if (allowed != type(uint).max) {
                require(allowed >= wad, "ERC20: Insufficient approval");
                unchecked { _setAllowance(src, msg.sender, allowed - wad); }
            }
        }

        return true;
    }

    /** @dev Creates `wad` tokens and assigns them to `dst`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     */
    /// if_succeeds {:msg "Mint - balance overflow"} old(_balanceOf[dst]) >= _balanceOf[dst];
    /// if_succeeds {:msg "Mint - supply overflow"} old(_totalSupply) >= _totalSupply;
    function _mint(address dst, uint wad) internal virtual returns (bool) {
        _balanceOf[dst] = _balanceOf[dst] + wad;
        _totalSupply = _totalSupply + wad;
        emit Transfer(address(0), dst, wad);

        return true;
    }

    /**
     * @dev Destroys `wad` tokens from `src`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `src` must have at least `wad` tokens.
     */
    /// if_succeeds {:msg "Burn - balance underflow"} old(_balanceOf[src]) <= _balanceOf[src];
    /// if_succeeds {:msg "Burn - supply underflow"} old(_totalSupply) <= _totalSupply;
    function _burn(address src, uint wad) internal virtual returns (bool) {
        unchecked {
            require(_balanceOf[src] >= wad, "ERC20: Insufficient balance");
            _balanceOf[src] = _balanceOf[src] - wad;
            _totalSupply = _totalSupply - wad;
            emit Transfer(src, address(0), wad);
        }

        return true;
    }
}
// File: @yield-protocol/utils-v2/contracts/token/IERC2612.sol



// SPDX-License-Identifier: MIT
// Code adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2237/
pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC2612 standard as defined in the EIP.
 *
 * Adds the {permit} method, which can be used to change one's
 * {IERC20-allowance} without having to send a transaction, by signing a
 * message. This allows users to spend tokens without having to hold Ether.
 *
 * See https://eips.ethereum.org/EIPS/eip-2612.
 */
interface IERC2612 {
    /**
     * @dev Sets `amount` as the allowance of `spender` over `owner`'s tokens,
     * given `owner`'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(address owner, address spender, uint256 amount, uint256 deadline, uint8 v, bytes32 r, bytes32 s) external;

    /**
     * @dev Returns the current ERC2612 nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);
}

// File: @yield-protocol/utils-v2/contracts/utils/RevertMsgExtractor.sol



// SPDX-License-Identifier: MIT
// Taken from https://github.com/sushiswap/BoringSolidity/blob/441e51c0544cf2451e6116fe00515e71d7c42e2c/contracts/BoringBatchable.sol

pragma solidity >=0.6.0;


library RevertMsgExtractor {
    /// @dev Helper function to extract a useful revert message from a failed call.
    /// If the returned data is malformed or not correctly abi encoded then this call can fail itself.
    function getRevertMsg(bytes memory returnData)
        internal pure
        returns (string memory)
    {
        // If the _res length is less than 68, then the transaction failed silently (without a revert message)
        if (returnData.length < 68) return "Transaction reverted silently";

        assembly {
            // Slice the sighash.
            returnData := add(returnData, 0x04)
        }
        return abi.decode(returnData, (string)); // All that remains is the revert string
    }
}
// File: @yield-protocol/yieldspace-v2/contracts/Math64x64.sol



// SPDX-License-Identifier: BUSL-1.1
/*
 *  Math 64.64 Smart Contract Library.  Copyright © 2019 by  Consulting.
 * Author: Mikhail Vladimirov <mikhail.vladimirov@gmail.com>
 */
pragma solidity 0.8.6;

/**
 * Smart contract library of mathematical functions operating with signed
 * 64.64-bit fixed point numbers.  Signed 64.64-bit fixed point number is
 * basically a simple fraction whose numerator is signed 128-bit integer and
 * denominator is 2^64.  As long as denominator is always the same, there is no
 * need to store it, thus in Solidity signed 64.64-bit fixed point numbers are
 * represented by int128 type holding only the numerator.
 */
library Math64x64 {
  /*
   * Minimum value signed 64.64-bit fixed point number may have. 
   */
  int128 private constant MIN_64x64 = -0x80000000000000000000000000000000;

  /*
   * Maximum value signed 64.64-bit fixed point number may have. 
   */
  int128 private constant MAX_64x64 = 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF;

  /**
   * Convert signed 256-bit integer number into signed 64.64-bit fixed point
   * number.  Revert on overflow.
   *
   * @param x signed 256-bit integer number
   * @return signed 64.64-bit fixed point number
   */
  function fromInt (int256 x) internal pure returns (int128) {
    unchecked {
      require (x >= -0x8000000000000000 && x <= 0x7FFFFFFFFFFFFFFF);
      return int128 (x << 64);
    }
  }

  /**
   * Convert signed 64.64 fixed point number into signed 64-bit integer number
   * rounding down.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64-bit integer number
   */
  function toInt (int128 x) internal pure returns (int64) {
    unchecked {
      return int64 (x >> 64);
    }
  }

  /**
   * Convert unsigned 256-bit integer number into signed 64.64-bit fixed point
   * number.  Revert on overflow.
   *
   * @param x unsigned 256-bit integer number
   * @return signed 64.64-bit fixed point number
   */
  function fromUInt (uint256 x) internal pure returns (int128) {
    unchecked {
      require (x <= 0x7FFFFFFFFFFFFFFF);
      return int128 (int256 (x << 64));
    }
  }

  /**
   * Convert signed 64.64 fixed point number into unsigned 64-bit integer
   * number rounding down.  Revert on underflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @return unsigned 64-bit integer number
   */
  function toUInt (int128 x) internal pure returns (uint64) {
    unchecked {
      require (x >= 0);
      return uint64 (uint128 (x >> 64));
    }
  }

  /**
   * Convert signed 128.128 fixed point number into signed 64.64-bit fixed point
   * number rounding down.  Revert on overflow.
   *
   * @param x signed 128.128-bin fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function from128x128 (int256 x) internal pure returns (int128) {
    unchecked {
      int256 result = x >> 64;
      require (result >= MIN_64x64 && result <= MAX_64x64);
      return int128 (result);
    }
  }

  /**
   * Convert signed 64.64 fixed point number into signed 128.128 fixed point
   * number.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 128.128 fixed point number
   */
  function to128x128 (int128 x) internal pure returns (int256) {
    unchecked {
      return int256 (x) << 64;
    }
  }

  /**
   * Calculate x + y.  Revert on overflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function add (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
      int256 result = int256(x) + y;
      require (result >= MIN_64x64 && result <= MAX_64x64);
      return int128 (result);
    }
  }

  /**
   * Calculate x - y.  Revert on overflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function sub (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
      int256 result = int256(x) - y;
      require (result >= MIN_64x64 && result <= MAX_64x64);
      return int128 (result);
    }
  }

  /**
   * Calculate x * y rounding down.  Revert on overflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function mul (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
      int256 result = int256(x) * y >> 64;
      require (result >= MIN_64x64 && result <= MAX_64x64);
      return int128 (result);
    }
  }

  /**
   * Calculate x * y rounding towards zero, where x is signed 64.64 fixed point
   * number and y is signed 256-bit integer number.  Revert on overflow.
   *
   * @param x signed 64.64 fixed point number
   * @param y signed 256-bit integer number
   * @return signed 256-bit integer number
   */
  function muli (int128 x, int256 y) internal pure returns (int256) {
    unchecked {
      if (x == MIN_64x64) {
        require (y >= -0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF &&
          y <= 0x1000000000000000000000000000000000000000000000000);
        return -y << 63;
      } else {
        bool negativeResult = false;
        if (x < 0) {
          x = -x;
          negativeResult = true;
        }
        if (y < 0) {
          y = -y; // We rely on overflow behavior here
          negativeResult = !negativeResult;
        }
        uint256 absoluteResult = mulu (x, uint256 (y));
        if (negativeResult) {
          require (absoluteResult <=
            0x8000000000000000000000000000000000000000000000000000000000000000);
          return -int256 (absoluteResult); // We rely on overflow behavior here
        } else {
          require (absoluteResult <=
            0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
          return int256 (absoluteResult);
        }
      }
    }
  }

  /**
   * Calculate x * y rounding down, where x is signed 64.64 fixed point number
   * and y is unsigned 256-bit integer number.  Revert on overflow.
   *
   * @param x signed 64.64 fixed point number
   * @param y unsigned 256-bit integer number
   * @return unsigned 256-bit integer number
   */
  function mulu (int128 x, uint256 y) internal pure returns (uint256) {
    unchecked {
      if (y == 0) return 0;

      require (x >= 0);

      uint256 lo = (uint256 (int256 (x)) * (y & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)) >> 64;
      uint256 hi = uint256 (int256 (x)) * (y >> 128);

      require (hi <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
      hi <<= 64;

      require (hi <=
        0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF - lo);
      return hi + lo;
    }
  }

  /**
   * Calculate x / y rounding towards zero.  Revert on overflow or when y is
   * zero.
   *
   * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function div (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
      require (y != 0);
      int256 result = (int256 (x) << 64) / y;
      require (result >= MIN_64x64 && result <= MAX_64x64);
      return int128 (result);
    }
  }

  /**
   * Calculate x / y rounding towards zero, where x and y are signed 256-bit
   * integer numbers.  Revert on overflow or when y is zero.
   *
   * @param x signed 256-bit integer number
   * @param y signed 256-bit integer number
   * @return signed 64.64-bit fixed point number
   */
  function divi (int256 x, int256 y) internal pure returns (int128) {
    unchecked {
      require (y != 0);

      bool negativeResult = false;
      if (x < 0) {
        x = -x; // We rely on overflow behavior here
        negativeResult = true;
      }
      if (y < 0) {
        y = -y; // We rely on overflow behavior here
        negativeResult = !negativeResult;
      }
      uint128 absoluteResult = divuu (uint256 (x), uint256 (y));
      if (negativeResult) {
        require (absoluteResult <= 0x80000000000000000000000000000000);
        return -int128 (absoluteResult); // We rely on overflow behavior here
      } else {
        require (absoluteResult <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
        return int128 (absoluteResult); // We rely on overflow behavior here
      }
    }
  }

  /**
   * Calculate x / y rounding towards zero, where x and y are unsigned 256-bit
   * integer numbers.  Revert on overflow or when y is zero.
   *
   * @param x unsigned 256-bit integer number
   * @param y unsigned 256-bit integer number
   * @return signed 64.64-bit fixed point number
   */
  function divu (uint256 x, uint256 y) internal pure returns (int128) {
    unchecked {
      require (y != 0);
      uint128 result = divuu (x, y);
      require (result <= uint128 (MAX_64x64));
      return int128 (result);
    }
  }

  /**
   * Calculate -x.  Revert on overflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function neg (int128 x) internal pure returns (int128) {
    unchecked {
      require (x != MIN_64x64);
      return -x;
    }
  }

  /**
   * Calculate |x|.  Revert on overflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function abs (int128 x) internal pure returns (int128) {
    unchecked {
      require (x != MIN_64x64);
      return x < 0 ? -x : x;
    }
  }

  /**
   * Calculate 1 / x rounding towards zero.  Revert on overflow or when x is
   * zero.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function inv (int128 x) internal pure returns (int128) {
    unchecked {
      require (x != 0);
      int256 result = int256 (0x100000000000000000000000000000000) / x;
      require (result >= MIN_64x64 && result <= MAX_64x64);
      return int128 (result);
    }
  }

  /**
   * Calculate arithmetics average of x and y, i.e. (x + y) / 2 rounding down.
   *
   * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function avg (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
      return int128 ((int256 (x) + int256 (y)) >> 1);
    }
  }

  /**
   * Calculate geometric average of x and y, i.e. sqrt (x * y) rounding down.
   * Revert on overflow or in case x * y is negative.
   *
   * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function gavg (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
      int256 m = int256 (x) * int256 (y);
      require (m >= 0);
      require (m <
          0x4000000000000000000000000000000000000000000000000000000000000000);
      return int128 (sqrtu (uint256 (m)));
    }
  }

  /**
   * Calculate x^y assuming 0^0 is 1, where x is signed 64.64 fixed point number
   * and y is unsigned 256-bit integer number.  Revert on overflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @param y uint256 value
   * @return signed 64.64-bit fixed point number
   */
  function pow (int128 x, uint256 y) internal pure returns (int128) {
    unchecked {
      bool negative = x < 0 && y & 1 == 1;

      uint256 absX = uint128 (x < 0 ? -x : x);
      uint256 absResult;
      absResult = 0x100000000000000000000000000000000;

      if (absX <= 0x10000000000000000) {
        absX <<= 63;
        while (y != 0) {
          if (y & 0x1 != 0) {
            absResult = absResult * absX >> 127;
          }
          absX = absX * absX >> 127;

          if (y & 0x2 != 0) {
            absResult = absResult * absX >> 127;
          }
          absX = absX * absX >> 127;

          if (y & 0x4 != 0) {
            absResult = absResult * absX >> 127;
          }
          absX = absX * absX >> 127;

          if (y & 0x8 != 0) {
            absResult = absResult * absX >> 127;
          }
          absX = absX * absX >> 127;

          y >>= 4;
        }

        absResult >>= 64;
      } else {
        uint256 absXShift = 63;
        if (absX < 0x1000000000000000000000000) { absX <<= 32; absXShift -= 32; }
        if (absX < 0x10000000000000000000000000000) { absX <<= 16; absXShift -= 16; }
        if (absX < 0x1000000000000000000000000000000) { absX <<= 8; absXShift -= 8; }
        if (absX < 0x10000000000000000000000000000000) { absX <<= 4; absXShift -= 4; }
        if (absX < 0x40000000000000000000000000000000) { absX <<= 2; absXShift -= 2; }
        if (absX < 0x80000000000000000000000000000000) { absX <<= 1; absXShift -= 1; }

        uint256 resultShift = 0;
        while (y != 0) {
          require (absXShift < 64);

          if (y & 0x1 != 0) {
            absResult = absResult * absX >> 127;
            resultShift += absXShift;
            if (absResult > 0x100000000000000000000000000000000) {
              absResult >>= 1;
              resultShift += 1;
            }
          }
          absX = absX * absX >> 127;
          absXShift <<= 1;
          if (absX >= 0x100000000000000000000000000000000) {
              absX >>= 1;
              absXShift += 1;
          }

          y >>= 1;
        }

        require (resultShift < 64);
        absResult >>= 64 - resultShift;
      }
      int256 result = negative ? -int256 (absResult) : int256 (absResult);
      require (result >= MIN_64x64 && result <= MAX_64x64);
      return int128 (result);
    }
  }

  /**
   * Calculate sqrt (x) rounding down.  Revert if x < 0.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function sqrt (int128 x) internal pure returns (int128) {
    unchecked {
      require (x >= 0);
      return int128 (sqrtu (uint256 (int256 (x)) << 64));
    }
  }

  /**
   * Calculate binary logarithm of x.  Revert if x <= 0.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function log_2 (int128 x) internal pure returns (int128) {
    unchecked {
      require (x > 0);

      int256 msb = 0;
      int256 xc = x;
      if (xc >= 0x10000000000000000) { xc >>= 64; msb += 64; }
      if (xc >= 0x100000000) { xc >>= 32; msb += 32; }
      if (xc >= 0x10000) { xc >>= 16; msb += 16; }
      if (xc >= 0x100) { xc >>= 8; msb += 8; }
      if (xc >= 0x10) { xc >>= 4; msb += 4; }
      if (xc >= 0x4) { xc >>= 2; msb += 2; }
      if (xc >= 0x2) msb += 1;  // No need to shift xc anymore

      int256 result = msb - 64 << 64;
      uint256 ux = uint256 (int256 (x)) << uint256 (127 - msb);
      for (int256 bit = 0x8000000000000000; bit > 0; bit >>= 1) {
        ux *= ux;
        uint256 b = ux >> 255;
        ux >>= 127 + b;
        result += bit * int256 (b);
      }

      return int128 (result);
    }
  }

  /**
   * Calculate natural logarithm of x.  Revert if x <= 0.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function ln (int128 x) internal pure returns (int128) {
    unchecked {
      require (x > 0);

      return int128 (int256 (
          uint256 (int256 (log_2 (x))) * 0xB17217F7D1CF79ABC9E3B39803F2F6AF >> 128));
    }
  }

  /**
   * Calculate binary exponent of x.  Revert on overflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function exp_2 (int128 x) internal pure returns (int128) {
    unchecked {
      require (x < 0x400000000000000000); // Overflow

      if (x < -0x400000000000000000) return 0; // Underflow

      uint256 result = 0x80000000000000000000000000000000;

      if (x & 0x8000000000000000 > 0)
        result = result * 0x16A09E667F3BCC908B2FB1366EA957D3E >> 128;
      if (x & 0x4000000000000000 > 0)
        result = result * 0x1306FE0A31B7152DE8D5A46305C85EDEC >> 128;
      if (x & 0x2000000000000000 > 0)
        result = result * 0x1172B83C7D517ADCDF7C8C50EB14A791F >> 128;
      if (x & 0x1000000000000000 > 0)
        result = result * 0x10B5586CF9890F6298B92B71842A98363 >> 128;
      if (x & 0x800000000000000 > 0)
        result = result * 0x1059B0D31585743AE7C548EB68CA417FD >> 128;
      if (x & 0x400000000000000 > 0)
        result = result * 0x102C9A3E778060EE6F7CACA4F7A29BDE8 >> 128;
      if (x & 0x200000000000000 > 0)
        result = result * 0x10163DA9FB33356D84A66AE336DCDFA3F >> 128;
      if (x & 0x100000000000000 > 0)
        result = result * 0x100B1AFA5ABCBED6129AB13EC11DC9543 >> 128;
      if (x & 0x80000000000000 > 0)
        result = result * 0x10058C86DA1C09EA1FF19D294CF2F679B >> 128;
      if (x & 0x40000000000000 > 0)
        result = result * 0x1002C605E2E8CEC506D21BFC89A23A00F >> 128;
      if (x & 0x20000000000000 > 0)
        result = result * 0x100162F3904051FA128BCA9C55C31E5DF >> 128;
      if (x & 0x10000000000000 > 0)
        result = result * 0x1000B175EFFDC76BA38E31671CA939725 >> 128;
      if (x & 0x8000000000000 > 0)
        result = result * 0x100058BA01FB9F96D6CACD4B180917C3D >> 128;
      if (x & 0x4000000000000 > 0)
        result = result * 0x10002C5CC37DA9491D0985C348C68E7B3 >> 128;
      if (x & 0x2000000000000 > 0)
        result = result * 0x1000162E525EE054754457D5995292026 >> 128;
      if (x & 0x1000000000000 > 0)
        result = result * 0x10000B17255775C040618BF4A4ADE83FC >> 128;
      if (x & 0x800000000000 > 0)
        result = result * 0x1000058B91B5BC9AE2EED81E9B7D4CFAB >> 128;
      if (x & 0x400000000000 > 0)
        result = result * 0x100002C5C89D5EC6CA4D7C8ACC017B7C9 >> 128;
      if (x & 0x200000000000 > 0)
        result = result * 0x10000162E43F4F831060E02D839A9D16D >> 128;
      if (x & 0x100000000000 > 0)
        result = result * 0x100000B1721BCFC99D9F890EA06911763 >> 128;
      if (x & 0x80000000000 > 0)
        result = result * 0x10000058B90CF1E6D97F9CA14DBCC1628 >> 128;
      if (x & 0x40000000000 > 0)
        result = result * 0x1000002C5C863B73F016468F6BAC5CA2B >> 128;
      if (x & 0x20000000000 > 0)
        result = result * 0x100000162E430E5A18F6119E3C02282A5 >> 128;
      if (x & 0x10000000000 > 0)
        result = result * 0x1000000B1721835514B86E6D96EFD1BFE >> 128;
      if (x & 0x8000000000 > 0)
        result = result * 0x100000058B90C0B48C6BE5DF846C5B2EF >> 128;
      if (x & 0x4000000000 > 0)
        result = result * 0x10000002C5C8601CC6B9E94213C72737A >> 128;
      if (x & 0x2000000000 > 0)
        result = result * 0x1000000162E42FFF037DF38AA2B219F06 >> 128;
      if (x & 0x1000000000 > 0)
        result = result * 0x10000000B17217FBA9C739AA5819F44F9 >> 128;
      if (x & 0x800000000 > 0)
        result = result * 0x1000000058B90BFCDEE5ACD3C1CEDC823 >> 128;
      if (x & 0x400000000 > 0)
        result = result * 0x100000002C5C85FE31F35A6A30DA1BE50 >> 128;
      if (x & 0x200000000 > 0)
        result = result * 0x10000000162E42FF0999CE3541B9FFFCF >> 128;
      if (x & 0x100000000 > 0)
        result = result * 0x100000000B17217F80F4EF5AADDA45554 >> 128;
      if (x & 0x80000000 > 0)
        result = result * 0x10000000058B90BFBF8479BD5A81B51AD >> 128;
      if (x & 0x40000000 > 0)
        result = result * 0x1000000002C5C85FDF84BD62AE30A74CC >> 128;
      if (x & 0x20000000 > 0)
        result = result * 0x100000000162E42FEFB2FED257559BDAA >> 128;
      if (x & 0x10000000 > 0)
        result = result * 0x1000000000B17217F7D5A7716BBA4A9AE >> 128;
      if (x & 0x8000000 > 0)
        result = result * 0x100000000058B90BFBE9DDBAC5E109CCE >> 128;
      if (x & 0x4000000 > 0)
        result = result * 0x10000000002C5C85FDF4B15DE6F17EB0D >> 128;
      if (x & 0x2000000 > 0)
        result = result * 0x1000000000162E42FEFA494F1478FDE05 >> 128;
      if (x & 0x1000000 > 0)
        result = result * 0x10000000000B17217F7D20CF927C8E94C >> 128;
      if (x & 0x800000 > 0)
        result = result * 0x1000000000058B90BFBE8F71CB4E4B33D >> 128;
      if (x & 0x400000 > 0)
        result = result * 0x100000000002C5C85FDF477B662B26945 >> 128;
      if (x & 0x200000 > 0)
        result = result * 0x10000000000162E42FEFA3AE53369388C >> 128;
      if (x & 0x100000 > 0)
        result = result * 0x100000000000B17217F7D1D351A389D40 >> 128;
      if (x & 0x80000 > 0)
        result = result * 0x10000000000058B90BFBE8E8B2D3D4EDE >> 128;
      if (x & 0x40000 > 0)
        result = result * 0x1000000000002C5C85FDF4741BEA6E77E >> 128;
      if (x & 0x20000 > 0)
        result = result * 0x100000000000162E42FEFA39FE95583C2 >> 128;
      if (x & 0x10000 > 0)
        result = result * 0x1000000000000B17217F7D1CFB72B45E1 >> 128;
      if (x & 0x8000 > 0)
        result = result * 0x100000000000058B90BFBE8E7CC35C3F0 >> 128;
      if (x & 0x4000 > 0)
        result = result * 0x10000000000002C5C85FDF473E242EA38 >> 128;
      if (x & 0x2000 > 0)
        result = result * 0x1000000000000162E42FEFA39F02B772C >> 128;
      if (x & 0x1000 > 0)
        result = result * 0x10000000000000B17217F7D1CF7D83C1A >> 128;
      if (x & 0x800 > 0)
        result = result * 0x1000000000000058B90BFBE8E7BDCBE2E >> 128;
      if (x & 0x400 > 0)
        result = result * 0x100000000000002C5C85FDF473DEA871F >> 128;
      if (x & 0x200 > 0)
        result = result * 0x10000000000000162E42FEFA39EF44D91 >> 128;
      if (x & 0x100 > 0)
        result = result * 0x100000000000000B17217F7D1CF79E949 >> 128;
      if (x & 0x80 > 0)
        result = result * 0x10000000000000058B90BFBE8E7BCE544 >> 128;
      if (x & 0x40 > 0)
        result = result * 0x1000000000000002C5C85FDF473DE6ECA >> 128;
      if (x & 0x20 > 0)
        result = result * 0x100000000000000162E42FEFA39EF366F >> 128;
      if (x & 0x10 > 0)
        result = result * 0x1000000000000000B17217F7D1CF79AFA >> 128;
      if (x & 0x8 > 0)
        result = result * 0x100000000000000058B90BFBE8E7BCD6D >> 128;
      if (x & 0x4 > 0)
        result = result * 0x10000000000000002C5C85FDF473DE6B2 >> 128;
      if (x & 0x2 > 0)
        result = result * 0x1000000000000000162E42FEFA39EF358 >> 128;
      if (x & 0x1 > 0)
        result = result * 0x10000000000000000B17217F7D1CF79AB >> 128;

      result >>= uint256 (int256 (63 - (x >> 64)));
      require (result <= uint256 (int256 (MAX_64x64)));

      return int128 (int256 (result));
    }
  }

  /**
   * Calculate natural exponent of x.  Revert on overflow.
   *
   * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
  function exp (int128 x) internal pure returns (int128) {
    unchecked {
      require (x < 0x400000000000000000); // Overflow

      if (x < -0x400000000000000000) return 0; // Underflow

      return exp_2 (
          int128 (int256 (x) * 0x171547652B82FE1777D0FFDA0D23A7D12 >> 128));
    }
  }

  /**
   * Calculate x / y rounding towards zero, where x and y are unsigned 256-bit
   * integer numbers.  Revert on overflow or when y is zero.
   *
   * @param x unsigned 256-bit integer number
   * @param y unsigned 256-bit integer number
   * @return unsigned 64.64-bit fixed point number
   */
  function divuu (uint256 x, uint256 y) private pure returns (uint128) {
    unchecked {
      require (y != 0);

      uint256 result;

      if (x <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)
        result = (x << 64) / y;
      else {
        uint256 msb = 192;
        uint256 xc = x >> 192;
        if (xc >= 0x100000000) { xc >>= 32; msb += 32; }
        if (xc >= 0x10000) { xc >>= 16; msb += 16; }
        if (xc >= 0x100) { xc >>= 8; msb += 8; }
        if (xc >= 0x10) { xc >>= 4; msb += 4; }
        if (xc >= 0x4) { xc >>= 2; msb += 2; }
        if (xc >= 0x2) msb += 1;  // No need to shift xc anymore

        result = (x << 255 - msb) / ((y - 1 >> msb - 191) + 1);
        require (result <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);

        uint256 hi = result * (y >> 128);
        uint256 lo = result * (y & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);

        uint256 xh = x >> 192;
        uint256 xl = x << 64;

        if (xl < lo) xh -= 1;
        xl -= lo; // We rely on overflow behavior here
        lo = hi << 128;
        if (xl < lo) xh -= 1;
        xl -= lo; // We rely on overflow behavior here

        assert (xh == hi >> 128);

        result += xl / y;
      }

      require (result <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
      return uint128 (result);
    }
  }

  /**
   * Calculate sqrt (x) rounding down, where x is unsigned 256-bit integer
   * number.
   *
   * @param x unsigned 256-bit integer number
   * @return unsigned 128-bit integer number
   */
  function sqrtu (uint256 x) private pure returns (uint128) {
    unchecked {
      if (x == 0) return 0;
      else {
        uint256 xx = x;
        uint256 r = 1;
        if (xx >= 0x100000000000000000000000000000000) { xx >>= 128; r <<= 64; }
        if (xx >= 0x10000000000000000) { xx >>= 64; r <<= 32; }
        if (xx >= 0x100000000) { xx >>= 32; r <<= 16; }
        if (xx >= 0x10000) { xx >>= 16; r <<= 8; }
        if (xx >= 0x100) { xx >>= 8; r <<= 4; }
        if (xx >= 0x10) { xx >>= 4; r <<= 2; }
        if (xx >= 0x8) { r <<= 1; }
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1;
        r = (r + x / r) >> 1; // Seven iterations should be enough
        uint256 r1 = x / r;
        return uint128 (r < r1 ? r : r1);
      }
    }
  }
}