#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 43; //four columns
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {5, 4, 3, 2}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {9, 8, 7, 6}; //connect to the column pinouts of the keypad

char key;

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup(){
  Serial.begin(9600);
}
  
void loop(){
    key = keypad.getKey();
    if(key){
      Serial.println(key);
    }
}