// Define pin numbers for LEDs
const int led_R = 2; // Red LED
const int led_Y = 3; // Yellow LED
const int led_G = 4; // Green LED

void setup() {
  // Initialize the LED pins as outputs
  pinMode(led_R, OUTPUT);
  pinMode(led_Y, OUTPUT);
  pinMode(led_G, OUTPUT);
}

void loop() {
  // Turn on the red LED
  digitalWrite(led_R, HIGH);
  delay(1000); // wait for 1 second
  // Turn off the red LED
  digitalWrite(led_R, LOW);
  delay(1000); // wait for 1 second

  // Turn on the yellow LED
  digitalWrite(led_Y, HIGH);
  delay(1000); // wait for 1 second
  // Turn off the yellow LED
  digitalWrite(led_Y, LOW);
  delay(1000); // wait for 1 second

  // Turn on the green LED
  digitalWrite(led_G, HIGH);
  delay(1000); // wait for 1 second
  // Turn off the green LED
  digitalWrite(led_G, LOW);
  delay(1000); // wait for 1 second
}