const int BTN_PINS[] = {11, 10, 9, 8};
const int LED_PINS[] = {5, 4, 3, 2};

void setup() {
  Serial.begin(115200);
  for (int i = 0; i < 4; i++) {
    pinMode(BTN_PINS[i], INPUT_PULLUP);
    pinMode(LED_PINS[i], OUTPUT);
  }
  Serial.print("Ready!");
}

void loop() {
  for (int i = 0; i < 4; i++) {
    if(digitalRead(BTN_PINS[i]) == LOW) {
      Serial.print("Button ");
      Serial.print(i + 1);
      Serial.println(" pressed.");
    }
  }
}