int GREEN = 3;
int YELLOW = 4;
int RED = 5;

void green_light() {
  digitalWrite(GREEN, HIGH);
  digitalWrite(YELLOW, LOW);
  digitalWrite(RED, LOW);
}

void yellow_light() {
  digitalWrite(GREEN, LOW);
  digitalWrite(YELLOW, HIGH);
  digitalWrite(RED, LOW);
}

void red_light() {
  digitalWrite(GREEN, LOW);
  digitalWrite(YELLOW, LOW);
  digitalWrite(RED, HIGH);
}

void red_yellow_light() {
  digitalWrite(GREEN, LOW);
  digitalWrite(YELLOW, HIGH);
  digitalWrite(RED, HIGH);
}

void blink_yellow_light() {
  digitalWrite(GREEN, LOW);
  digitalWrite(RED, LOW);
  for (int i = 1; i < 10; i++) {
    digitalWrite(YELLOW, LOW);
    delay(500);
    digitalWrite(YELLOW, HIGH);
    delay(500);
  }
}

void setup() {
  Serial.begin(9600);
  pinMode(GREEN, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(RED, OUTPUT);
  Serial.println("Start");
}

void loop() {
  digitalWrite(RED, HIGH);
  digitalWrite(YELLOW, HIGH);
  digitalWrite(GREEN, HIGH);
  digitalWrite(12, HIGH);
  blink_yellow_light();
}