const int pines[] = {13, 12, 14, 27};
const int LEDs = 4;

int tiempo = 400; 

void setup() {
  for (int i = 0; i < LEDs; i++){
    pinMode(pines[i], OUTPUT);
  }
}

void loop() {
  for (int i = 0; i < LEDs; i++){
    digitalWrite(pines[i], HIGH);
    delay(tiempo);
    digitalWrite(pines[i], LOW);
  }

  for (int i = LEDs - 1; i >= 0; i--){
    digitalWrite(pines[i], HIGH);
    delay(tiempo);
    digitalWrite(pines[i], LOW);
  }
}