contract StandardToken is ERC20, SeaToken {
 
  mapping (address => mapping (address => uint256)) allowed;
 
  /*
    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;
  }
 
  /*
  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 Roman Lanskoj's 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;
  }
 
  /*
  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];
}
}
/* Implementation of the basic standard token.
 https://github.com/ethereum/EIPs/issues/20
 */
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;
}

/*
 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 Roman Lanskoj's tokens to be spent.
 */