int BUTTON_1 = 8;
int BUTTON_2 = 9;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600); 
  pinMode(BUTTON_1, INPUT_PULLUP);
  pinMode(BUTTON_2, INPUT_PULLUP);
}

int delay_time = 100;
int prevButtonState = 1;
int currButtonState = 1;

void loop() {
  // put your main code here, to run repeatedly:
  delay(delay_time);

  prevButtonState = currButtonState;
  currButtonState = digitalRead(BUTTON_1);
  if((currButtonState != prevButtonState) && (currButtonState == LOW)){
    Serial.println("Button 1 pressed");
    return;
  }
  currButtonState = digitalRead(BUTTON_2);
  if((currButtonState != prevButtonState) && (currButtonState == LOW)){
    Serial.println("Button 2 pressed");
    return;
  }
}