int myPins[]= {8, 9, 12, 13};
void setup() {
  // put your setup code here, to run once:
  for (int i=0 ;i< sizeof(myPins); i++){
      pinMode(myPins[i], OUTPUT);

  }
}

void loop() {
  // put your main code here, to run repeatedly:
  for (int i=0 ;i< sizeof(myPins); i++){
      digitalWrite(myPins[i], HIGH);
      delay(500);
  }

  for (int i=0 ;i< sizeof(myPins); i++){
      digitalWrite(myPins[i], LOW);
      delay(500);
  
  }
}