library SafeMath {

	  /**
	  * @dev Multiplies two numbers, throws on overflow.
	  */

	  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
	    // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
	    // benefit is lost if 'b' is also tested.
	    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
	  if (a == 0) {
	      return 0;
      }
	      c = a * b;
	      assert(c / a == b);
	      return c;
	  }

	  /**
	  * @dev Integer division of two numbers, truncating the quotient.
	  */

	  function div(uint256 a, uint256 b) internal pure returns (uint256) {
	    // assert(b > 0); // Solidity automatically throws when dividing by 0
	    // uint256 c = a / b;
	    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
	    return a / b;
	  }

	    /**
	    * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
	    */

	    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
	        assert(b <= a);
	        return a - b;
	    }

	    /**
	    * @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 SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure.
 * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
function div(uint256 a, uint256 b) internal pure returns (uint256) {
	    // assert(b > 0); // Solidity automatically throws when dividing by 0
	    // uint256 c = a / b;
	    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
	    return a / b;
	  }
/**
 	  * @dev Integer division of two numbers, truncating the quotient.
 	  */