contract StandardToken is ERC20, BasicToken {

	mapping (address => mapping (address => uint256)) internal 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 amount of tokens to be transferred
	*/
	function transferFrom(
		address _from,
		address _to,
		uint256 _value
	)
	public
	returns (bool)
	{
		require(_to != address(0), "Invl");
		require(_value <= balances[_from], "NSF");
		require(_value <= allowed[_from][msg.sender], "NFAllowance");

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

	/**
	* @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
	* Beware that changing an allowance with this method brings the risk that someone may use both the old
	* and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
	* race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
	* https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
	* @param _spender The address which will spend the funds.
	* @param _value The amount of tokens to be spent.
	*/
	function approve(address _spender, uint256 _value) public returns (bool) {
		allowed[msg.sender][_spender] = _value;
		emit 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 specifying the amount of tokens still available for the spender.
	*/
	function allowance(
		address _owner,
		address _spender
	)
	public
	view
	returns (uint256)
	{
		return allowed[_owner][_spender];
	}

	/**
	* @dev Increase the amount of tokens that an owner allowed to a spender.
	* approve should be called when allowed[_spender] == 0. To increment
	* allowed value is better to use this function to avoid 2 calls (and wait until
	* the first transaction is mined)
	* From MonolithDAO Token.sol
	* @param _spender The address which will spend the funds.
	* @param _addedValue The amount of tokens to increase the allowance by.
	*/
	function increaseApproval(
		address _spender,
		uint256 _addedValue
	)
	public
	returns (bool)
	{
		allowed[msg.sender][_spender] = (
		allowed[msg.sender][_spender].add(_addedValue));
		emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
		return true;
	}

	/**
	* @dev Decrease the amount of tokens that an owner allowed to a spender.
	* approve should be called when allowed[_spender] == 0. To decrement
	* allowed value is better to use this function to avoid 2 calls (and wait until
	* the first transaction is mined)
	* From MonolithDAO Token.sol
	* @param _spender The address which will spend the funds.
	* @param _subtractedValue The amount of tokens to decrease the allowance by.
	*/
	function decreaseApproval(
		address _spender,
		uint256 _subtractedValue
	)
	public
	returns (bool)
	{
		uint256 oldValue = allowed[msg.sender][_spender];
		if (_subtractedValue > oldValue) {
			allowed[msg.sender][_spender] = 0;
		} else {
			allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
		}
		emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
		return true;
	}

}
/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * https://github.com/ethereum/EIPs/issues/20
 * Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
function transferFrom(
	address _from,
	address _to,
	uint256 _value
)
public
returns (bool)
{
	require(_to != address(0), "Invl");
	require(_value <= balances[_from], "NSF");
	require(_value <= allowed[_from][msg.sender], "NFAllowance");

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

/**
 	* @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 amount of tokens to be transferred
 	*/