void setup() {

  pinMode (red, OUTPUT);

  pinMode (yellow, OUTPUT);

  pinMode (green, OUTPUT);
}

  void loop() {

  digitalWrite(red, HIGH);

  digitalWrite(yellow, LOW); digitalWrite (green, LOW);

  delay (2000);

  digitalWrite(red, LOW);

  digitalWrite(yellow, HIGH); delay(1000);

  digitalWrite (yellow, LOW); digitalWrite (green, HIGH); delay(2000);

  digitalWrite (green, LOW);

  }