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);
	}
}
function abs(int256 a) internal pure returns (int256) {
	require(a != MIN_INT256);
	return a < 0 ? -a : a;
}

/**
 	 * @dev Converts to absolute value, and fails on overflow.
 	 */