const int ledPins[] = {4,5,6,7}; 
const int numLEDs = 4; 

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

void loop() {
  for (int i = 0; i < numLEDs; i++) {
    digitalWrite(ledPins[i], HIGH); 
    delay(1000);
            digitalWrite(ledPins[i], LOW);

    delay(1000);

  // }

  }
}