contract StandardToken is ERC20, SafeMath {

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

    /// @dev Returns number of tokens owned by given address.
    /// @param _owner Address of token owner.
    function balanceOf(address _owner) public constant returns (uint256 balance) {
        return balances[_owner];
    }

    /// @dev Transfers sender's tokens to a given address. Returns success.
    /// @param _to Address of token receiver.
    /// @param _value Number of tokens to transfer.
    function transfer(address _to, uint256 _value) public returns (bool) {
        if (balances[msg.sender] >= _value && _value > 0) {
            balances[msg.sender] = safeSub(balances[msg.sender], _value);
            balances[_to] = safeAdd(balances[_to], _value);
            Transfer(msg.sender, _to, _value);
            return true;
        } else return false;
    }

    /// @dev Allows allowed third party to transfer tokens from one address to another. Returns success.
    /// @param _from Address from where tokens are withdrawn.
    /// @param _to Address to where tokens are sent.
    /// @param _value Number of tokens to transfer.
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && _value > 0) {
            balances[_to] = safeAdd(balances[_to], _value);
            balances[_from] = safeSub(balances[_from], _value);
            allowed[_from][msg.sender] = safeSub(allowed[_from][msg.sender], _value);
            Transfer(_from, _to, _value);
            return true;
        } else return false;
    }

    /// @dev Sets approved amount of tokens for spender. Returns success.
    /// @param _spender Address of allowed account.
    /// @param _value Number of approved tokens.
    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    /// @dev Returns number of allowed tokens for given address.
    /// @param _owner Address of token owner.
    /// @param _spender Address of token spender.
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }
}
function transfer(address _to, uint256 _value) public returns (bool) {
        if (balances[msg.sender] >= _value && _value > 0) {
            balances[msg.sender] = safeSub(balances[msg.sender], _value);
            balances[_to] = safeAdd(balances[_to], _value);
            Transfer(msg.sender, _to, _value);
            return true;
        } else return false;
    }
/// @dev Transfers sender's tokens to a given address. Returns success.
/// @param _to Address of token receiver.
/// @param _value Number of tokens to transfer.