contract StandardToken is ERC20, BasicToken {

	mapping (address => mapping (address => uint256)) allowed;

	/**
	* @dev Transfer tokens from one address to another
	* @param _from address The address which you want to send tokens from
	* @param _to address The address which you want to transfer to
	* @param _value uint256 the amout of tokens to be transfered
	*/
	function transferFrom(address _from, address _to, uint256 _value) returns (bool) {
	  
		var _allowance = allowed[_from][msg.sender];

		// Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
		// require (_value <= _allowance);

		balances[_to] = balances[_to].add(_value);
		balances[_from] = balances[_from].sub(_value);
		allowed[_from][msg.sender] = _allowance.sub(_value);
		Transfer(_from, _to, _value);
		return true;
	}

	/**
	* @dev Aprove the passed address to spend the specified amount of tokens on behalf of msg.sender.
	* @param _spender The address which will spend the funds.
	* @param _value The amount of tokens to be spent.
	*/
	function approve(address _spender, uint256 _value) returns (bool) {

		// To change the approve amount you first have to reduce the addresses`
		//  allowance to zero by calling `approve(_spender, 0)` if it is not
		//  already 0 to mitigate the race condition described here:
		//  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
		require((_value == 0) || (allowed[msg.sender][_spender] == 0));

		allowed[msg.sender][_spender] = _value;
		Approval(msg.sender, _spender, _value);
		return true;
	}

	/**
	* @dev Function to check the amount of tokens that an owner allowed to a spender.
	* @param _owner address The address which owns the funds.
	* @param _spender address The address which will spend the funds.
	* @return A uint256 specifing the amount of tokens still available for the spender.
	*/
	function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
		return allowed[_owner][_spender];
	}

}
/**
 * @title Standard ERC20 token
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
		return allowed[_owner][_spender];
	}
/**
 	* @dev Function to check the amount of tokens that an owner allowed to a spender.
 	* @param _owner address The address which owns the funds.
 	* @param _spender address The address which will spend the funds.
 	* @return A uint256 specifing the amount of tokens still available for the spender.
 	*/