constexpr int buttonPin = 3;  // the number of the pushbutton pin

// variables will change:
byte buttonState;  // variable for reading the pushbutton status
byte lastButtonState = 1;

void setup() {
  Serial.begin(9600);
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop() {
  // read the state of the pushbutton value:
  buttonState = buttonStatus();
  if (buttonState != lastButtonState) {
    lastButtonState = buttonState;
    if (buttonState == HIGH) {
      Serial.println("OFF");
    } else  {
      Serial.println("ON");
    }
  }
}



boolean buttonStatus() {
  static unsigned long lastChange = 0;
  static byte state = HIGH;
  static byte lastState = HIGH;
  byte actState = digitalRead(buttonPin);
  if (actState != lastState) {
    lastChange = millis();
    lastState  = actState;
  }
  if (state != lastState && millis() - lastChange > 30) {
    state = lastState;
  }
  return state;
}