pragma solidity ^0.4.21;

contract IYFIV {

    uint256 public totalSupply;


    function balanceOf(address _owner) public view returns (uint256 balance);


    function transfer(address _to, uint256 _value) public returns (bool success);


    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);


    function approve(address _spender, uint256 _value) public returns (bool success);


    function allowance(address _owner, address _spender) public view returns (uint256 remaining);


    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

library SafeMath {


    function mul(uint256 a, uint256 b) internal pure returns (uint256) {

        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b);
        return c;
    }


    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0);
        uint256 c = a / b;
        return c;
    }


    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;
        return c;
    }


    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);
        return c;
    }


    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }
}


contract YFIV is IYFIV {
    using SafeMath for uint256;

    mapping(address => uint256) public balances;
    mapping(address => mapping(address => uint256)) public allowed;

    string public name;
    uint8 public decimals;
    string public symbol;

    function YFIV(
        uint256 _initialAmount,
        string _tokenName,
        uint8 _decimalUnits,
        string _tokenSymbol
    ) public {
        balances[msg.sender] = _initialAmount;
        totalSupply = _initialAmount;
        name = _tokenName;
        decimals = _decimalUnits;
        symbol = _tokenSymbol;
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        require(_to != address(0));
        require(balances[msg.sender] >= _value);

        balances[msg.sender] = balances[msg.sender].sub(_value);

        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        uint256 allowance = allowed[_from][msg.sender];
        require(balances[_from] >= _value && allowance >= _value);
        require(_to != address(0));

        balances[_to] = balances[_to].add(_value);

        balances[_from] = balances[_from].sub(_value);

        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);

        emit Transfer(_from, _to, _value);
        return true;
    }

    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }

    function approve(address _spender, uint256 _value) public returns (bool success) {
        require(_spender != address(0));
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
        require(_spender != address(0));
        return allowed[_owner][_spender];
    }
}