const int BUTTON_PIN = 7;  
const int LED_PIN =  3;   


int buttonState = 0;   

void setup() {
  
  pinMode(LED_PIN, OUTPUT);
  
  
  pinMode(BUTTON_PIN, INPUT_PULLUP);
}

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

  
  if(buttonState == LOW)         
    digitalWrite(LED_PIN, HIGH); 
  else                           
    digitalWrite(LED_PIN, LOW);
}