#define RED_LED_PIN 2
#define GREEN_LED_PIN 3
#define YELLOW_LED_PIN 4

void setup() {
  // Initialize the digital pins as outputs.
  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(YELLOW_LED_PIN, OUTPUT);
}

void loop() {
  // Turn on Red and Yellow LEDs, turn off Green LED
  digitalWrite(RED_LED_PIN, HIGH);
  digitalWrite(YELLOW_LED_PIN, HIGH);
  digitalWrite(GREEN_LED_PIN, LOW);
  delay(1000); // Wait for 1 second

  // Turn off Red and Yellow LEDs, turn on Green LED
  digitalWrite(RED_LED_PIN, LOW);
  digitalWrite(YELLOW_LED_PIN, LOW);
  digitalWrite(GREEN_LED_PIN, HIGH);
  delay(1000); // Wait for 1 second
}