const int LED[4] = {25, 27, 12, 13};

void setup() {
  // Serial.begin(9600);
  for (int i = 0; i < 4; i++)
    pinMode(LED[i], OUTPUT);
}

void loop() {
  for (int i = 0; i < 4; i++)
  {
    digitalWrite(LED[i], 1);
    digitalWrite(LED[i - 1], 0);
    // Serial.print(LED[i]);
    // Serial.print(" , ");
    // Serial.println(LED[i - 1]);
    delay(1000);
  }
  digitalWrite(LED[3], 0);
}