//simple button input_pullup
int button1 = 4;

void setup()
{
  Serial.begin(9600);
  pinMode(button1, INPUT_PULLUP);
}
void loop()
{
  byte buttonState = digitalRead(button1);

  if(buttonState == LOW){
    Serial.println("Button is pressed");
  } 
  else{
    Serial.println("Button is not pressed");
  }
  delay(100);
}