const byte interruptPin = 3;
volatile uint8_t count = 0;

void setup() {
  Serial.begin(115200);
  pinMode(interruptPin, INPUT);
  attachInterrupt(digitalPinToInterrupt(interruptPin), on_button_pressed, RISING);

  pinMode(2, INPUT);
  attachInterrupt(digitalPinToInterrupt(2), on_button_pressed_2, RISING);
}

void on_button_pressed() {
  count++;
}

void on_button_pressed_2() {
  count++;
}

void loop() {
  Serial.println(count);
}