const int ledPin1 = 2;  // Pin connected to the first LED
const int ledPin2 = 4;  // Pin connected to the second LED
const int ledPin3 = 15;  // Pin connected to the third LED
const int ledPin4 = 18; // Pin connected to the fourth LED

void setup() {
  pinMode(ledPin1, OUTPUT);
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  pinMode(ledPin4, OUTPUT);
}

void loop() {
  // Turn on all LEDs
  digitalWrite(ledPin1, HIGH);
  delay(100); // Wait for 1 second
  digitalWrite(ledPin2, HIGH);
   delay(100); // Wait for 1 second
  digitalWrite(ledPin3, HIGH);
   delay(100); // Wait for 1 second
  digitalWrite(ledPin4, HIGH);
  delay(100); // Wait for 1 second

  // Turn off all LEDs
  digitalWrite(ledPin1, LOW);
  digitalWrite(ledPin2, LOW);
  digitalWrite(ledPin3, LOW);
  digitalWrite(ledPin4, LOW);
  delay(100); // Wait for 1 second
}