int motorPin=3;
void setup() {
  pinMode(motorPin, OUTPUT);
  Serial.begin (9600);
  while (! Serial);
  Serial.println("Speed 0 to 10");

}

void loop()
{

  if (Serial.available ())
  {
  int speed= Serial.parseInt();
  if (speed >= 0 && speed <= 250)
  {
  analogWrite(motorPin, speed);
  }
  }
}