void setup() {
  // put your setup code here, to run once:
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  for (int i = 2; i <= 5; i++) {
    digitalWrite(i, HIGH);
    delay(250);
    digitalWrite(i, LOW);
    delay(250);
  }

 
  for (int i = 5; i >= 2; i--) {
    digitalWrite(i, HIGH);
    delay(250);
    digitalWrite(i, LOW);
    delay(250);
  }

}