void loop() {
  int numArray[6] = { 3,5,6,9,10,11 };
  int randomIndex = rand() % 6;
  int randomValue = numArray[randomIndex];

    analogWrite(randomValue, brightness);
    brightness = brightness + fadeStep;
    delay(10);

    if (brightness == 255 || brightness == 0){
      fadeStep = -fadeStep;
    }
    delay(10);
}