DC Motor Variable Speed code

const int motorOut = 9;
void setup() {
  pinMode(motorOut, OUTPUT);
  Serial.begin(9600);
  while(! Serial)
  {
    Serial.println("Speed = 0 to 255");//user prompt for speed
  }
}

void loop() {
  if(Serial.available() > 0)
  {
    int motorSpeed = Serial.parseInt();//takes input from the serial monitor
    if(motorSpeed >= 1 && motorSpeed <= 255)//ensures a value that is usable
    {
      analogWrite(motorOut, motorSpeed);
    }
    else if(motorSpeed == -1)//command to stop movement
    {
      analogWrite(motorOut, 0);
    }
  }
}