// LED pin definitions
int redLED = 19;
int yellowLED = 18;
int greenLED = 5;

void setup() {
  pinMode(redLED, OUTPUT);
  pinMode(yellowLED, OUTPUT);
  pinMode(greenLED, OUTPUT);
}

void loop() {
  // GREEN ON
  digitalWrite(greenLED, HIGH);
  digitalWrite(yellowLED, LOW);
  digitalWrite(redLED, LOW);
  delay(3000);   // 3 seconds

  // YELLOW ON
  digitalWrite(greenLED, LOW);
  digitalWrite(yellowLED, HIGH);
  digitalWrite(redLED, LOW);
  delay(2000);   // 2 seconds

  // RED ON
  digitalWrite(greenLED, LOW);
  digitalWrite(yellowLED, LOW);
  digitalWrite(redLED, HIGH);
  delay(3000);   // 3 seconds
}