 
 
 
-String left()
+String left(int argument)
 {
   turnMotorsOn();
 

  int argument = getArgumentFromInput(input);
  
  if(command == "check battery status") {
    result = checkBatteryStatus();
  } else if(command == "forward") {
    result = forward();
  } else if(command == "backward") {
    result = backward();
  } else if(command == "left") {
    result = left();
  } else if(command == "right") {
    result = right();
  } else if(command == "stop") {
    result = halt();
  } else {
    result = "unknown command: " + command + ", arg: " + argument;
  }

  return "ok";
}

String backward(int argument)
{
  turnMotorsOn();
  
