const int btn = 12;  
const int green = 5;      
const int red = 18;      
const int yellow = 19;       

int state = 0;            
bool Pressed = false;

void setup() {
  pinMode(btn, INPUT_PULLUP);  
  pinMode(green, OUTPUT);
  pinMode(red, OUTPUT);
  pinMode(yellow, OUTPUT);
  
  digitalWrite(green, LOW);
  digitalWrite(red, LOW);
  digitalWrite(yellow, LOW);
}

void loop() {
  if (digitalRead(btn) == LOW) { 
    delay(100);
    if (!Pressed) {  
      state = (state + 1) % 3; 
      updateLights();
      Pressed = true;
    }
  } else {
    Pressed = false;  
  }
}

void updateLights() {
  digitalWrite(green, state == 0 ? HIGH : LOW);
  digitalWrite(red, state == 1 ? HIGH : LOW);
  digitalWrite(yellow, state == 2 ? HIGH : LOW);
}