#include <Keyboard.h>

Keyboard keyboard;

#define BUTTON 13

void setup() {
  pinMode(BUTTON, INPUT_PULLUP);
  keyboard.begin(); // Initialize the Keyboard library
}

void loop() {
  static int lastButtonState = HIGH;
  int buttonState = digitalRead(BUTTON);

  if (buttonState == LOW && lastButtonState == HIGH) {
    // Button was pressed
    keyboard.write('a');
  }

  lastButtonState = buttonState;
}