#define LED_PIN 15
  #define BUTTON_PIN 4
  
  void setup() {
    pinMode(LED_PIN, OUTPUT);
    pinMode(BUTTON_PIN, INPUT);
  }
  void loop() {
    if(digitalRead(BUTTON_PIN) == HIGH)
      {
        digitalWrite(LED_PIN,HIGH);
      }
    else {
      digitalWrite(LED_PIN,LOW);
    }
  }