const int buttonPin = 4; 
const int ledPin = 15;   

int buttonState = 0;     
int lastButtonState = 0; 
int ledState = LOW;      

void setup() {
  pinMode(ledPin, OUTPUT);     
  pinMode(buttonPin, INPUT);  
}

void loop() {
  
  buttonState = digitalRead(buttonPin);

  
  if (buttonState == HIGH && lastButtonState == LOW) {
   
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }
    
    digitalWrite(ledPin, ledState);
  }

  
  lastButtonState = buttonState;
}