#include <Keypad.h>

// Define the number of rows and columns of the keypad
const byte ROWS = 4;
const byte COLS = 4;

// Define the keymap
char keys[ROWS][COLS] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'@', '0', '#', '%'}
};

// Define the pin connections for rows and columns
byte rowPins[ROWS] = {9, 8, 7, 6};
byte colPins[COLS] = {5, 4, 3, 2};

// Create an instance of the Keypad class
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup() {
  // Begin serial communication at a baud rate of 9600
  Serial.begin(9600);
}

void loop() {
  // Get the key pressed
  char key = keypad.getKey();

  // If a key is pressed, print it to the Serial Monitor
  if (key) {
    Serial.print("Key pressed: ");
    Serial.println(key);
  }
}