int RED = 2;
int  YELLOW = 9;
int  GREEN = 13;

void setup() {
  pinMode(RED, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(GREEN, OUTPUT);
}

void loop() {
  digitalWrite(RED, HIGH);
  delay(1000);

  digitalWrite(RED, LOW);
  digitalWrite(YELLOW, HIGH);
  delay(1000);

  digitalWrite(YELLOW, LOW);
  digitalWrite(GREEN, HIGH);
  delay(1000);

  digitalWrite(YELLOW, HIGH);
    digitalWrite(GREEN, LOW);


  delay(1000);
  digitalWrite(YELLOW, LOW);
  digitalWrite(GREEN, LOW);
}