int redPin = 13;
int yellowPin = 12;
int greenPin = 10;
void setup() {
  pinMode(redPin, INPUT);
  pinMode(yellowPin, INPUT);
  pinMode(greenPin, INPUT);
}
void loop() {
  redLight();
  yellowLight();
  greenLight();
  yellowLight();
  delay(1000);
}
void allLightsOff() {
  digitalWrite(redPin, HIGH);
  digitalWrite(yellowPin, HIGH);
  digitalWrite(greenPin, HIGH);
}
void redLight() {
  allLightsOff();
  digitalWrite(redPin, LOW);
}
void yellowLight() {
  allLightsOff();
  digitalWrite(yellowPin, LOW);
}
void greenLight() {
  allLightsOff();
  digitalWrite(greenPin, LOW);
}
void blinkingYellow() {
  for(int Yellow = 0; Yellow < 6; Yellow++){
      digitalWrite(yellowPin, Yellow % 2);
      delay(500);
  }
}