const int ledPins[] = {18, 19, 21, 22}; // LED pins
int counter = 0;

void setup() {
  // Initialize the LED pins as outputs
  for (int i = 0; i < 4; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  // Display the counter value on the LEDs
  for (int i = 0; i < 4; i++) {
    digitalWrite(ledPins[i], (counter >> i) & 1);
  }

  // Increment the counter
  counter++;
  if (counter > 15) { // Reset the counter after 15 (4-bit counter)
    counter = 0;
  }

  delay(1000); // Wait for 1 second
}