library SafeMath {
	/**
	 * SafeMath mul function
	 * @dev function for safe multiply, throws on overflow.
	 **/
	function mul(uint256 a, uint256 b) internal pure returns (uint256) {
		uint256 c = a * b;
		assert(a == 0 || c / a == b);
		return c;
	}

	/**
	 * SafeMath div funciotn
	 * @dev function for safe devide, throws on overflow.
	 **/
	function div(uint256 a, uint256 b) internal pure returns (uint256) {
		uint256 c = a / b;
		return c;
	}

	/**
	 * SafeMath sub function
	 * @dev function for safe subtraction, throws on overflow.
	 **/
	function sub(uint256 a, uint256 b) internal pure returns (uint256) {
		assert(b <= a);
		return a - b;
	}
	
	/**
	 * SafeMath add function
	 * @dev Adds two numbers, throws on overflow.
	 */
	function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
		c = a + b;
		assert(c >= a);
		return c;
	}
}
/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 * @notice https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/math/SafeMath.sol
 */
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
	uint256 c = a * b;
	assert(a == 0 || c / a == b);
	return c;
}

/**
 	 * SafeMath mul function
 	 * @dev function for safe multiply, throws on overflow.
 	 **/