function AirDrop(uint256 _startTime, uint256 _endTime, uint _airDropAmount, address _tokenAddress) public {
        require(_startTime >= now &&
            _endTime >= _startTime &&
            _airDropAmount > 0 &&
            _tokenAddress != address(0)
        );
        startTime = _startTime;
        endTime = _endTime;
        erc20 = ERC20BasicInterface(_tokenAddress);
        uint tokenDecimals = erc20.decimals();
        airDropAmount = _airDropAmount.mul(10 ** tokenDecimals);
    }