// File: contracts/COS/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.6;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// File: contracts/COS/COS.sol



// SPDX-License-Identifier: MIT

/*

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*/

pragma solidity ^0.8.17;

import "./DividendPayingToken.sol";
import "./IterableMapping.sol";
import "./Ownable.sol";
import "./IDex.sol";

library Address {
    function sendValue(address payable recipient, uint256 amount) internal {
        require(
            address(this).balance >= amount,
            "Address: insufficient balance"
        );

        (bool success, ) = recipient.call{value: amount}("");
        require(
            success,
            "Address: unable to send value, recipient may have reverted"
        );
    }
}

contract COS is ERC20, Ownable {
    using Address for address payable;

    IRouter public router;
    address public pair;

    bool public tradingEnabled;
    uint256 public constant startTime = 1694615400; //13 september, 18 PM utc
    uint256 public startBlock;

    bool private swapping;
    bool public swapEnabled = true;

    COSDividendTracker public dividendTracker;
    uint256 public Optimization = 803120086119310562983196;

    address public constant deadWallet =
        0x000000000000000000000000000000000000dEaD;
    address public marketingWallet = 0x33D9A744C2DceE5fBa650763075D93D873587D0D;
    address public teamWallet = 0xEE80e04B7dc1c99284C49D5D4E2b09999039c41d;
    address public constant USDT = 0xdAC17F958D2ee523a2206206994597C13D831ec7;

    uint256 public swapTokensAtAmount = 1e8 * 10 ** 18;

    struct Taxes {
        uint256 rewards;
        uint256 marketing;
        uint256 team;
    }

    Taxes public buyTaxes = Taxes(0, 3, 2);
    Taxes public sellTaxes = Taxes(2, 2, 2);
    Taxes public transferTaxes = Taxes(0, 0, 0);

    uint256 public gasForProcessing = 300000;

    mapping(address => bool) private _isExcludedFromFees;
    mapping(address => bool) public automatedMarketMakerPairs;

    event ExcludeFromFees(address indexed account, bool isExcluded);
    event ExcludeMultipleAccountsFromFees(address[] accounts, bool isExcluded);
    event SetAutomatedMarketMakerPair(address indexed pair, bool indexed value);
    event GasForProcessingUpdated(
        uint256 indexed newValue,
        uint256 indexed oldValue
    );
    event SendDividends(uint256 tokensSwapped, uint256 amount);
    event ProcessedDividendTracker(
        uint256 iterations,
        uint256 claims,
        uint256 lastProcessedIndex,
        bool indexed automatic,
        uint256 gas,
        address indexed processor
    );

    constructor() ERC20("Call of Shib", "COS") {
        dividendTracker = new COSDividendTracker();

        IRouter _router = IRouter(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
        address _pair = IFactory(_router.factory()).createPair(
            address(this),
            _router.WETH()
        );

        router = _router;
        pair = _pair;

        _setAutomatedMarketMakerPair(_pair, true);

        address newOwner = 0x07AdB060bB9FAB15a49010d09F79fdAd819904eb;
        // exclude from receiving dividends

        excludeFromFees(marketingWallet, true);
        excludeFromFees(teamWallet, true);
        excludeFromFees(address(this), true);

        _tokengeneration(newOwner, 1_000_000_000_000_000 * (10 ** 18));
        swapTokensAtAmount = totalSupply() / 1000;
        transferOwnership(newOwner);
    }

    receive() external payable {}

    function processDividendTracker(uint256 gas) external {
        (
            uint256 iterations,
            uint256 claims,
            uint256 lastProcessedIndex
        ) = dividendTracker.process(gas);
        emit ProcessedDividendTracker(
            iterations,
            claims,
            lastProcessedIndex,
            false,
            gas,
            tx.origin
        );
    }

    function setBuyTaxes(
        uint256 _rewards,
        uint256 _marketing,
        uint256 _team
    ) external onlyOwner {
        require(
            _rewards + _marketing + _team <= 10,
            "Taxes cannot be more than 10%"
        );
        buyTaxes = Taxes(_rewards, _marketing, _team);
    }

    function setSellTaxes(
        uint256 _rewards,
        uint256 _marketing,
        uint256 _team
    ) external onlyOwner {
        require(
            _rewards + _marketing + _team <= 10,
            "Taxes cannot be more than 10%"
        );
        sellTaxes = Taxes(_rewards, _marketing, _team);
    }

    function setTransferTaxes(
        uint256 _rewards,
        uint256 _marketing,
        uint256 _team
    ) external onlyOwner {
        require(
            _rewards + _marketing + _team <= 10,
            "Taxes cannot be more than 10%"
        );
        transferTaxes = Taxes(_rewards, _marketing, _team);
    }

    function claim() external {
        dividendTracker.processAccount(payable(msg.sender), false);
    }

    function excludeFromFees(address account, bool excluded) public onlyOwner {
        require(
            _isExcludedFromFees[account] != excluded,
            "COS: Account is already the value of 'excluded'"
        );
        _isExcludedFromFees[account] = excluded;

        emit ExcludeFromFees(account, excluded);
    }

    function excludeMultipleAccountsFromFees(
        address[] calldata accounts,
        bool excluded
    ) public onlyOwner {
        for (uint256 i = 0; i < accounts.length; i++) {
            _isExcludedFromFees[accounts[i]] = excluded;
        }
        emit ExcludeMultipleAccountsFromFees(accounts, excluded);
    }

    function excludeFromDividends(
        address account,
        bool value
    ) external onlyOwner {
        dividendTracker.excludeFromDividends(account, value);
    }

    function setMarketingWallet(address newWallet) external onlyOwner {
        require(newWallet != address(0), "Fee Address cannot be zero address");
        marketingWallet = newWallet;
    }

    function setTeamWallet(address newWallet) external onlyOwner {
        require(newWallet != address(0), "Fee Address cannot be zero address");
        teamWallet = newWallet;
    }

    function setSwapTokensAtAmount(uint256 amount) external onlyOwner {
        require(
            amount >= totalSupply() / 1_000_000,
            "cant set swap threshold to less than 1/1000000 of total supply"
        );
        require(
            amount <= totalSupply() / 1_00,
            "cant set swap threshold to more than 1/100 of total supply"
        );
        swapTokensAtAmount = amount;
    }

    function setSwapEnabled(bool _enabled) external onlyOwner {
        swapEnabled = _enabled;
    }

    function setMinBalanceForDividends(uint256 amount) external onlyOwner {
        dividendTracker.setMinBalanceForDividends(amount);
    }

    function _setAutomatedMarketMakerPair(address newPair, bool value) private {
        require(
            automatedMarketMakerPairs[newPair] != value,
            "COS: Automated market maker pair is already set to that value"
        );
        automatedMarketMakerPairs[newPair] = value;

        if (value) {
            dividendTracker.excludeFromDividends(newPair, true);
        }

        emit SetAutomatedMarketMakerPair(newPair, value);
    }

    function setGasForProcessing(uint256 newValue) external onlyOwner {
        require(
            newValue >= 200000 && newValue <= 500000,
            "COS: gasForProcessing must be between 200,000 and 500,000"
        );
        require(
            newValue != gasForProcessing,
            "COS: Cannot update gasForProcessing to same value"
        );
        emit GasForProcessingUpdated(newValue, gasForProcessing);
        gasForProcessing = newValue;
    }

    function setClaimWait(uint256 claimWait) external onlyOwner {
        dividendTracker.updateClaimWait(claimWait);
    }

    function getClaimWait() external view returns (uint256) {
        return dividendTracker.claimWait();
    }

    function getTotalDividendsDistributed() external view returns (uint256) {
        return dividendTracker.totalDividendsDistributed();
    }

    function isExcludedFromFees(address account) public view returns (bool) {
        return _isExcludedFromFees[account];
    }

    function withdrawableDividendOf(
        address account
    ) public view returns (uint256) {
        return dividendTracker.withdrawableDividendOf(account);
    }

    function getCurrentRewardToken() external view returns (string memory) {
        return dividendTracker.getCurrentRewardToken();
    }

    function dividendTokenBalanceOf(
        address account
    ) public view returns (uint256) {
        return dividendTracker.balanceOf(account);
    }

    function getAccountDividendsInfo(
        address account
    )
        external
        view
        returns (
            address,
            int256,
            int256,
            uint256,
            uint256,
            uint256,
            uint256,
            uint256
        )
    {
        return dividendTracker.getAccount(account);
    }

    function getAccountDividendsInfoAtIndex(
        uint256 index
    )
        external
        view
        returns (
            address,
            int256,
            int256,
            uint256,
            uint256,
            uint256,
            uint256,
            uint256
        )
    {
        return dividendTracker.getAccountAtIndex(index);
    }

    function getLastProcessedIndex() external view returns (uint256) {
        return dividendTracker.getLastProcessedIndex();
    }

    function getNumberOfDividendTokenHolders() external view returns (uint256) {
        return dividendTracker.getNumberOfTokenHolders();
    }

    function getFee(
        bool isSell,
        bool isTransfer
    ) public view returns (Taxes memory target) {
        if (block.timestamp > startTime + 3.5 hours) {
            target = isSell ? sellTaxes : isTransfer ? transferTaxes : buyTaxes;
        } else if (block.timestamp > startTime + 2.5 hours) {
            target = isSell ? Taxes(0, 10, 0) : isTransfer
                ? transferTaxes
                : Taxes(0, 5, 0);
        } else if (block.timestamp > startTime + 1.5 hours) {
            target = isSell ? Taxes(0, 15, 0) : isTransfer
                ? transferTaxes
                : Taxes(0, 5, 0);
        } else if (block.timestamp > startTime + 1 hours) {
            target = isSell ? Taxes(0, 20, 0) : isTransfer
                ? transferTaxes
                : Taxes(0, 5, 0);
        } else if (block.timestamp > startTime + 30 minutes) {
            target = isSell ? Taxes(0, 25, 0) : isTransfer
                ? transferTaxes
                : Taxes(0, 5, 0);
        } else if (block.number < startBlock + 4) {
            target = Taxes(0, 98, 0);
        } else {
            target = isSell ? Taxes(0, 30, 0) : isTransfer
                ? transferTaxes
                : Taxes(0, 5, 0);
        }
    }

    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal override {
        require(from != address(0), "COS: transfer from the zero address");
        require(to != address(0), "COS: transfer to the zero address");

        if (amount == 0) {
            super._transfer(from, to, 0);
            return;
        }

        bool canSwap = balanceOf(address(this)) >= swapTokensAtAmount;

        if (
            canSwap &&
            !swapping &&
            swapEnabled &&
            !automatedMarketMakerPairs[from] &&
            !_isExcludedFromFees[from] &&
            !_isExcludedFromFees[to]
        ) {
            swapping = true;
            swapAndLiquify(swapTokensAtAmount);
            swapping = false;
        }

        bool takeFee = !swapping;

        if (_isExcludedFromFees[from] || _isExcludedFromFees[to]) {
            takeFee = false;
        } else {
            require(block.timestamp > startTime, "Trading is not enabled yet!");
            if (startBlock == 0) {
                startBlock = block.number;
            }
        }

        if (takeFee) {
            bool isSell;
            bool isTransfer;
            if (automatedMarketMakerPairs[to]) {
                isSell = true;
            } else if (automatedMarketMakerPairs[from]) {
                isTransfer = false;
            } else {
                isTransfer = true;
            }
            Taxes memory fees = getFee(isSell, isTransfer);
            uint256 totalFee = fees.rewards + fees.marketing + fees.team;
            uint256 fee;
            if (totalFee > 0) {
                fee = (amount * totalFee) / 100;
                super._transfer(from, address(this), fee);
                amount -= fee;
            }
        }

        super._transfer(from, to, amount);

        try dividendTracker.setBalance(from, balanceOf(from)) {} catch {}
        try dividendTracker.setBalance(to, balanceOf(to)) {} catch {}
        if (!swapping) {
            uint256 gas = gasForProcessing;
            try dividendTracker.process(gas) returns (
                uint256 iterations,
                uint256 claims,
                uint256 lastProcessedIndex
            ) {
                emit ProcessedDividendTracker(
                    iterations,
                    claims,
                    lastProcessedIndex,
                    true,
                    gas,
                    tx.origin
                );
            } catch {}
        }
    }

    function swapAndLiquify(uint256 tokens) private {
        if (tokens == 0) return;

        Taxes memory buyT = buyTaxes;
        Taxes memory sellT = sellTaxes;
        Taxes memory transferT = transferTaxes;

        uint totalRewardFee = buyT.rewards + sellT.rewards + transferT.rewards;
        uint totalMarketingFee = buyT.marketing +
            sellT.marketing +
            transferT.marketing;
        uint totalTeamFee = buyT.team + sellT.team + transferT.team;
        uint256 denominator = totalRewardFee + totalMarketingFee + totalTeamFee;
        if (denominator == 0) return;

        //avoid stack too deep
        {
            uint USDTShare = (tokens * (totalMarketingFee + totalTeamFee)) /
                denominator;
            if (USDTShare > 0) {
                swapTokensForUSDT(USDTShare);
                uint USDTBalance = IERC20(USDT).balanceOf(address(this));
                IERC20(USDT).transfer(
                    marketingWallet,
                    (USDTBalance * totalMarketingFee) /
                        (totalMarketingFee + totalTeamFee)
                );
                IERC20(USDT).transfer(
                    teamWallet,
                    IERC20(USDT).balanceOf(address(this))
                );
                tokens -= USDTShare;
            }
        }
        if (tokens == 0) return;

        //avoid stack too deep
        {
            swapTokensForETH(tokens);
            uint received = address(this).balance;
            (bool success, ) = address(dividendTracker).call{value: received}(
                ""
            );
            if (success) emit SendDividends(tokens, received);
        }
    }

    function swapTokensForUSDT(uint256 tokenAmount) private {
        address[] memory path = new address[](3);
        path[0] = address(this);
        path[1] = router.WETH();
        path[2] = USDT;
        _approve(address(this), address(router), tokenAmount);
        // make the swap
        router.swapExactTokensForTokensSupportingFeeOnTransferTokens(
            tokenAmount,
            0, // accept any amount of ETH
            path,
            address(this),
            block.timestamp
        );
    }

    function swapTokensForETH(uint256 tokenAmount) private {
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = router.WETH();
        _approve(address(this), address(router), tokenAmount);
        // make the swap
        router.swapExactTokensForETHSupportingFeeOnTransferTokens(
            tokenAmount,
            0, // accept any amount of ETH
            path,
            address(this),
            block.timestamp
        );
    }

    function withdrawToken(address tokenAddress) external onlyOwner {
        IERC20(tokenAddress).transfer(
            msg.sender,
            IERC20(tokenAddress).balanceOf(address(this))
        );
    }

    function withdrawETH() external onlyOwner {
        uint256 ETHbalance = address(this).balance;
        payable(owner()).sendValue(ETHbalance);
    }
}

contract COSDividendTracker is Ownable, DividendPayingToken {
    using SafeMath for uint256;
    using SafeMathInt for int256;
    using IterableMapping for IterableMapping.Map;

    IterableMapping.Map private tokenHoldersMap;
    uint256 public lastProcessedIndex;

    mapping(address => bool) public excludedFromDividends;

    mapping(address => uint256) public lastClaimTimes;

    uint256 public claimWait;
    uint256 public minimumTokenBalanceForDividends;

    event ExcludeFromDividends(address indexed account, bool value);
    event ClaimWaitUpdated(uint256 indexed newValue, uint256 indexed oldValue);

    event Claim(
        address indexed account,
        uint256 amount,
        bool indexed automatic
    );

    constructor()
        DividendPayingToken("COS_Dividend_Tracker", "COS_Dividend_Tracker")
    {
        claimWait = 3600;
        minimumTokenBalanceForDividends = 1 * (10 ** decimals());
    }

    function _transfer(address, address, uint256) internal pure override {
        require(false, "COS_Dividend_Tracker: No transfers allowed");
    }

    function setMinBalanceForDividends(uint256 amount) external onlyOwner {
        minimumTokenBalanceForDividends = amount * 10 ** decimals();
    }

    function excludeFromDividends(
        address account,
        bool value
    ) external onlyOwner {
        require(excludedFromDividends[account] != value);
        excludedFromDividends[account] = value;
        if (value == true) {
            _setBalance(account, 0);
            tokenHoldersMap.remove(account);
        } else {
            _setBalance(account, balanceOf(account));
            tokenHoldersMap.set(account, balanceOf(account));
        }
        emit ExcludeFromDividends(account, value);
    }

    function updateClaimWait(uint256 newClaimWait) external onlyOwner {
        require(
            newClaimWait >= 3600 && newClaimWait <= 86400,
            "COS_Dividend_Tracker: claimWait must be updated to between 1 and 24 hours"
        );
        require(
            newClaimWait != claimWait,
            "COS_Dividend_Tracker: Cannot update claimWait to same value"
        );
        emit ClaimWaitUpdated(newClaimWait, claimWait);
        claimWait = newClaimWait;
    }

    function getLastProcessedIndex() external view returns (uint256) {
        return lastProcessedIndex;
    }

    function getNumberOfTokenHolders() external view returns (uint256) {
        return tokenHoldersMap.keys.length;
    }

    function getCurrentRewardToken() external view returns (string memory) {
        return IERC20Metadata(rewardToken).name();
    }

    function getAccount(
        address _account
    )
        public
        view
        returns (
            address account,
            int256 index,
            int256 iterationsUntilProcessed,
            uint256 withdrawableDividends,
            uint256 totalDividends,
            uint256 lastClaimTime,
            uint256 nextClaimTime,
            uint256 secondsUntilAutoClaimAvailable
        )
    {
        account = _account;

        index = tokenHoldersMap.getIndexOfKey(account);

        iterationsUntilProcessed = -1;

        if (index >= 0) {
            if (uint256(index) > lastProcessedIndex) {
                iterationsUntilProcessed = index.sub(
                    int256(lastProcessedIndex)
                );
            } else {
                uint256 processesUntilEndOfArray = tokenHoldersMap.keys.length >
                    lastProcessedIndex
                    ? tokenHoldersMap.keys.length.sub(lastProcessedIndex)
                    : 0;

                iterationsUntilProcessed =
                    index +
                    (int256(processesUntilEndOfArray));
            }
        }

        withdrawableDividends = withdrawableDividendOf(account);
        totalDividends = accumulativeDividendOf(account);

        lastClaimTime = lastClaimTimes[account];

        nextClaimTime = lastClaimTime > 0 ? lastClaimTime + (claimWait) : 0;

        secondsUntilAutoClaimAvailable = nextClaimTime > block.timestamp
            ? nextClaimTime.sub(block.timestamp)
            : 0;
    }

    function getAccountAtIndex(
        uint256 index
    )
        public
        view
        returns (
            address,
            int256,
            int256,
            uint256,
            uint256,
            uint256,
            uint256,
            uint256
        )
    {
        if (index >= tokenHoldersMap.size()) {
            return (
                0x0000000000000000000000000000000000000000,
                -1,
                -1,
                0,
                0,
                0,
                0,
                0
            );
        }

        address account = tokenHoldersMap.getKeyAtIndex(index);

        return getAccount(account);
    }

    function canAutoClaim(uint256 lastClaimTime) private view returns (bool) {
        if (lastClaimTime > block.timestamp) {
            return false;
        }

        return block.timestamp.sub(lastClaimTime) >= claimWait;
    }

    function setBalance(address account, uint256 newBalance) public onlyOwner {
        if (excludedFromDividends[account]) {
            return;
        }

        if (newBalance >= minimumTokenBalanceForDividends) {
            _setBalance(account, newBalance);
            tokenHoldersMap.set(account, newBalance);
        } else {
            _setBalance(account, 0);
            tokenHoldersMap.remove(account);
        }

        processAccount(payable(account), true);
    }

    function process(uint256 gas) public returns (uint256, uint256, uint256) {
        uint256 numberOfTokenHolders = tokenHoldersMap.keys.length;

        if (numberOfTokenHolders == 0) {
            return (0, 0, lastProcessedIndex);
        }

        uint256 _lastProcessedIndex = lastProcessedIndex;

        uint256 gasUsed = 0;

        uint256 gasLeft = gasleft();

        uint256 iterations = 0;
        uint256 claims = 0;

        while (gasUsed < gas && iterations < numberOfTokenHolders) {
            _lastProcessedIndex++;

            if (_lastProcessedIndex >= tokenHoldersMap.keys.length) {
                _lastProcessedIndex = 0;
            }

            address account = tokenHoldersMap.keys[_lastProcessedIndex];

            if (canAutoClaim(lastClaimTimes[account])) {
                if (processAccount(payable(account), true)) {
                    claims++;
                }
            }

            iterations++;

            uint256 newGasLeft = gasleft();

            if (gasLeft > newGasLeft) {
                gasUsed = gasUsed + (gasLeft.sub(newGasLeft));
            }

            gasLeft = newGasLeft;
        }

        lastProcessedIndex = _lastProcessedIndex;

        return (iterations, claims, lastProcessedIndex);
    }

    function processAccount(
        address payable account,
        bool automatic
    ) public onlyOwner returns (bool) {
        uint256 amount = _withdrawDividendOfUser(account);

        if (amount > 0) {
            lastClaimTimes[account] = block.timestamp;
            emit Claim(account, amount, automatic);
            return true;
        }

        return false;
    }
}

// File: contracts/COS/DividendPayingToken.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.17;

import "./ERC20.sol";
import "./IERC20.sol";
import "./SafeMath.sol";
import "./DividendPayingTokenInterface.sol";
import "./Ownable.sol";
import "./IDex.sol";

contract DividendPayingToken is ERC20, DividendPayingTokenInterface, Ownable {
    using SafeMath for uint256;
    using SafeMathUint for uint256;
    using SafeMathInt for int256;

    // With `magnitude`, we can properly distribute dividends even if the amount of received ether is small.
    // For more discussion about choosing the value of `magnitude`,
    //  see https://github.com/ethereum/EIPs/issues/1726#issuecomment-472352728
    uint256 internal constant magnitude = 2 ** 128;

    IRouter public router;
    address public rewardToken;

    uint256 internal magnifiedDividendPerShare;

    // About dividendCorrection:
    // If the token balance of a `_user` is never changed, the dividend of `_user` can be computed with:
    //   `dividendOf(_user) = dividendPerShare * balanceOf(_user)`.
    // When `balanceOf(_user)` is changed (via new tokens/burning/transferring tokens),
    //   `dividendOf(_user)` should not be changed,
    //   but the computed value of `dividendPerShare * balanceOf(_user)` is changed.
    // To keep the `dividendOf(_user)` unchanged, we add a correction term:
    //   `dividendOf(_user) = dividendPerShare * balanceOf(_user) + dividendCorrectionOf(_user)`,
    //   where `dividendCorrectionOf(_user)` is updated whenever `balanceOf(_user)` is changed:
    //   `dividendCorrectionOf(_user) = dividendPerShare * (old balanceOf(_user)) - (new balanceOf(_user))`.
    // So now `dividendOf(_user)` returns the same value before and after `balanceOf(_user)` is changed.
    mapping(address => int256) internal magnifiedDividendCorrections;
    mapping(address => uint256) internal withdrawnDividends;

    uint256 public totalDividendsDistributed;

    constructor(
        string memory _name,
        string memory _symbol
    ) ERC20(_name, _symbol) {
        IRouter _router = IRouter(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
        router = _router;
        rewardToken = 0xdAC17F958D2ee523a2206206994597C13D831ec7;
    }

    /// @dev Distributes dividends whenever ether is paid to this contract.
    receive() external payable {
        distributeDividends();
    }

    function distributeDividends() public payable override {
        require(totalSupply() > 0);

        if (msg.value > 0) {
            magnifiedDividendPerShare = magnifiedDividendPerShare.add(
                (msg.value).mul(magnitude) / totalSupply()
            );
            emit DividendsDistributed(msg.sender, msg.value);

            totalDividendsDistributed = totalDividendsDistributed.add(
                msg.value
            );
        }
    }

    /// @notice Withdraws the ether distributed to the sender.
    /// @dev It emits a `DividendWithdrawn` event if the amount of withdrawn ether is greater than 0.
    function _withdrawDividendOfUser(
        address payable user
    ) internal returns (uint256) {
        uint256 _withdrawableDividend = withdrawableDividendOf(user);
        if (_withdrawableDividend > 0) {
            withdrawnDividends[user] = withdrawnDividends[user].add(
                _withdrawableDividend
            );
            emit DividendWithdrawn(user, _withdrawableDividend);
            if (rewardToken != router.WETH()) {
                bool success = swapBnbForCustomToken(
                    user,
                    _withdrawableDividend
                );
                if (!success) {
                    (bool secondSuccess, ) = user.call{
                        value: _withdrawableDividend,
                        gas: 3000
                    }("");
                    if (!secondSuccess) {
                        withdrawnDividends[user] = withdrawnDividends[user].sub(
                            _withdrawableDividend
                        );
                        return 0;
                    }
                }
            } else {
                (bool success, ) = user.call{
                    value: _withdrawableDividend,
                    gas: 3000
                }("");
                if (!success) {
                    withdrawnDividends[user] = withdrawnDividends[user].sub(
                        _withdrawableDividend
                    );
                    return 0;
                }
            }
            return _withdrawableDividend;
        }
        return 0;
    }

    function setRewardToken(address newToken) external onlyOwner {
        rewardToken = newToken;
    }

    function swapBnbForCustomToken(
        address user,
        uint256 amt
    ) internal returns (bool) {
        address[] memory path = new address[](2);
        path[0] = router.WETH();
        path[1] = rewardToken;

        try
            router.swapExactETHForTokens{value: amt}(
                0,
                path,
                user,
                block.timestamp + 2
            )
        {
            return true;
        } catch {
            return false;
        }
    }

    /// @notice View the amount of dividend in wei that an address can withdraw.
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` can withdraw.
    function dividendOf(address _owner) public view override returns (uint256) {
        return withdrawableDividendOf(_owner);
    }

    /// @notice View the amount of dividend in wei that an address can withdraw.
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` can withdraw.
    function withdrawableDividendOf(
        address _owner
    ) public view override returns (uint256) {
        return accumulativeDividendOf(_owner).sub(withdrawnDividends[_owner]);
    }

    /// @notice View the amount of dividend in wei that an address has withdrawn.
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` has withdrawn.
    function withdrawnDividendOf(
        address _owner
    ) public view override returns (uint256) {
        return withdrawnDividends[_owner];
    }

    /// @notice View the amount of dividend in wei that an address has earned in total.
    /// @dev accumulativeDividendOf(_owner) = withdrawableDividendOf(_owner) + withdrawnDividendOf(_owner)
    /// = (magnifiedDividendPerShare * balanceOf(_owner) + magnifiedDividendCorrections[_owner]) / magnitude
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` has earned in total.
    function accumulativeDividendOf(
        address _owner
    ) public view override returns (uint256) {
        return
            magnifiedDividendPerShare
                .mul(balanceOf(_owner))
                .toInt256Safe()
                .add(magnifiedDividendCorrections[_owner])
                .toUint256Safe() / magnitude;
    }

    /// @dev Internal function that transfer tokens from one address to another.
    /// Update magnifiedDividendCorrections to keep dividends unchanged.
    /// @param from The address to transfer from.
    /// @param to The address to transfer to.
    /// @param value The amount to be transferred.
    function _transfer(
        address from,
        address to,
        uint256 value
    ) internal virtual override {
        require(false);

        int256 _magCorrection = magnifiedDividendPerShare
            .mul(value)
            .toInt256Safe();
        magnifiedDividendCorrections[from] = magnifiedDividendCorrections[from]
            .add(_magCorrection);
        magnifiedDividendCorrections[to] = magnifiedDividendCorrections[to].sub(
            _magCorrection
        );
    }

    /// Update magnifiedDividendCorrections to keep dividends unchanged.
    /// @param account The account that will receive the created tokens.
    /// @param value The amount that will be created.
    function _tokengeneration(
        address account,
        uint256 value
    ) internal override {
        super._tokengeneration(account, value);

        magnifiedDividendCorrections[account] = magnifiedDividendCorrections[
            account
        ].sub((magnifiedDividendPerShare.mul(value)).toInt256Safe());
    }

    /// @dev Internal function that burns an amount of the token of a given account.
    /// Update magnifiedDividendCorrections to keep dividends unchanged.
    /// @param account The account whose tokens will be burnt.
    /// @param value The amount that will be burnt.
    function _burn(address account, uint256 value) internal override {
        super._burn(account, value);

        magnifiedDividendCorrections[account] = magnifiedDividendCorrections[
            account
        ].add((magnifiedDividendPerShare.mul(value)).toInt256Safe());
    }

    function _setBalance(address account, uint256 newBalance) internal {
        uint256 currentBalance = balanceOf(account);

        if (newBalance > currentBalance) {
            uint256 rewardtokensAmount = newBalance.sub(currentBalance);
            _tokengeneration(account, rewardtokensAmount);
        } else if (newBalance < currentBalance) {
            uint256 burnAmount = currentBalance.sub(newBalance);
            _burn(account, burnAmount);
        }
    }
}

// File: contracts/COS/DividendPayingTokenInterface.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.6;

/// @title Dividend-Paying Token Interface
/// @author Roger Wu (https://github.com/roger-wu)
/// @dev An interface for a dividend-paying token contract.
interface DividendPayingTokenInterface {
    /// @notice View the amount of dividend in wei that an address can withdraw.
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` can withdraw.
    function dividendOf(address _owner) external view returns (uint256);

    function distributeDividends() external payable;

    /// @notice View the amount of dividend in wei that an address can withdraw.
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` can withdraw.
    function withdrawableDividendOf(
        address _owner
    ) external view returns (uint256);

    /// @notice View the amount of dividend in wei that an address has withdrawn.
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` has withdrawn.
    function withdrawnDividendOf(
        address _owner
    ) external view returns (uint256);

    /// @notice View the amount of dividend in wei that an address has earned in total.
    /// @dev accumulativeDividendOf(_owner) = withdrawableDividendOf(_owner) + withdrawnDividendOf(_owner)
    /// @param _owner The address of a token holder.
    /// @return The amount of dividend in wei that `_owner` has earned in total.
    function accumulativeDividendOf(
        address _owner
    ) external view returns (uint256);

    /// @dev This event MUST emit when ether is distributed to token holders.
    /// @param from The address which sends ether to this contract.
    /// @param weiAmount The amount of distributed ether in wei.
    event DividendsDistributed(address indexed from, uint256 weiAmount);

    /// @dev This event MUST emit when an address withdraws their dividend.
    /// @param to The address which withdraws ether from this contract.
    /// @param weiAmount The amount of withdrawn ether in wei.
    event DividendWithdrawn(address indexed to, uint256 weiAmount);
}

// File: contracts/COS/ERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.6;

import "./IERC20.sol";
import "./Context.sol";
import "./SafeMath.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 {_tokengeneration}.
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * 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.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    using SafeMath for uint256;

    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

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

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

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

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

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(
        address spender,
        uint256 amount
    ) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @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:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(
            sender,
            _msgSender(),
            _allowances[sender][_msgSender()].sub(
                amount,
                "ERC20: transfer amount exceeds allowance"
            )
        );
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(
        address spender,
        uint256 addedValue
    ) public virtual returns (bool) {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender].add(addedValue)
        );
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(
        address spender,
        uint256 subtractedValue
    ) public virtual returns (bool) {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender].sub(
                subtractedValue,
                "ERC20: decreased allowance below zero"
            )
        );
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(
            amount,
            "ERC20: transfer amount exceeds balance"
        );
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /*
            _tokengeneration is an internal function in ERC20.sol that is only called here to generate the total supply first time,
            and CANNOT be called ever again
        */
    function _tokengeneration(
        address account,
        uint256 amount
    ) internal virtual {
        require(account != address(0), "ERC20: new tokens to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(
            amount,
            "ERC20: burn amount exceeds balance"
        );
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// File: contracts/COS/IDex.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.6;

interface IPair {
    function sync() external;
}

interface IFactory {
    function createPair(
        address tokenA,
        address tokenB
    ) external returns (address pair);

    function getPair(
        address tokenA,
        address tokenB
    ) external view returns (address pair);
}

interface IRouter {
    function factory() external pure returns (address);

    function WETH() external pure returns (address);

    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    )
        external
        payable
        returns (uint amountToken, uint amountETH, uint liquidity);

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;

    function swapExactETHForTokens(
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external payable returns (uint[] memory amounts);

    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;

    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external payable;
}

// File: contracts/COS/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.6;

/**
 * @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);
}

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
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: contracts/COS/IterableMapping.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;

library IterableMapping {
    // Iterable mapping from address to uint;
    struct Map {
        address[] keys;
        mapping(address => uint) values;
        mapping(address => uint) indexOf;
        mapping(address => bool) inserted;
    }

    function get(Map storage map, address key) internal view returns (uint) {
        return map.values[key];
    }

    function getIndexOfKey(Map storage map, address key) internal view returns (int) {
        if(!map.inserted[key]) {
            return -1;
        }
        return int(map.indexOf[key]);
    }

    function getKeyAtIndex(Map storage map, uint index) internal view returns (address) {
        return map.keys[index];
    }



    function size(Map storage map) internal view returns (uint) {
        return map.keys.length;
    }

    function set(Map storage map, address key, uint val) internal {
        if (map.inserted[key]) {
            map.values[key] = val;
        } else {
            map.inserted[key] = true;
            map.values[key] = val;
            map.indexOf[key] = map.keys.length;
            map.keys.push(key);
        }
    }

    function remove(Map storage map, address key) internal {
        if (!map.inserted[key]) {
            return;
        }

        delete map.inserted[key];
        delete map.values[key];

        uint index = map.indexOf[key];
        uint lastIndex = map.keys.length - 1;
        address lastKey = map.keys[lastIndex];

        map.indexOf[lastKey] = index;
        delete map.indexOf[key];

        map.keys[index] = lastKey;
        map.keys.pop();
    }
}
// File: contracts/COS/Ownable.sol



pragma solidity ^0.8.6;

// SPDX-License-Identifier: MIT License

import "./Context.sol";

contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(_owner == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: contracts/COS/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.6;

library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

/**
 * @title SafeMathInt
 * @dev Math operations for int256 with overflow safety checks.
 */
library SafeMathInt {
    int256 private constant MIN_INT256 = int256(1) << 255;
    int256 private constant MAX_INT256 = ~(int256(1) << 255);

    /**
     * @dev Multiplies two int256 variables and fails on overflow.
     */
    function mul(int256 a, int256 b) internal pure returns (int256) {
        int256 c = a * b;

        // Detect overflow when multiplying MIN_INT256 with -1
        require(c != MIN_INT256 || (a & MIN_INT256) != (b & MIN_INT256));
        require((b == 0) || (c / b == a));
        return c;
    }

    /**
     * @dev Division of two int256 variables and fails on overflow.
     */
    function div(int256 a, int256 b) internal pure returns (int256) {
        // Prevent overflow when dividing MIN_INT256 by -1
        require(b != -1 || a != MIN_INT256);

        // Solidity already throws when dividing by 0.
        return a / b;
    }

    /**
     * @dev Subtracts two int256 variables and fails on overflow.
     */
    function sub(int256 a, int256 b) internal pure returns (int256) {
        int256 c = a - b;
        require((b >= 0 && c <= a) || (b < 0 && c > a));
        return c;
    }

    /**
     * @dev Adds two int256 variables and fails on overflow.
     */
    function add(int256 a, int256 b) internal pure returns (int256) {
        int256 c = a + b;
        require((b >= 0 && c >= a) || (b < 0 && c < a));
        return c;
    }

    /**
     * @dev Converts to absolute value, and fails on overflow.
     */
    function abs(int256 a) internal pure returns (int256) {
        require(a != MIN_INT256);
        return a < 0 ? -a : a;
    }

    function toUint256Safe(int256 a) internal pure returns (uint256) {
        require(a >= 0);
        return uint256(a);
    }
}

/**
 * @title SafeMathUint
 * @dev Math operations with safety checks that revert on error
 */
library SafeMathUint {
    function toInt256Safe(uint256 a) internal pure returns (int256) {
        int256 b = int256(a);
        require(b >= 0);
        return b;
    }
}