#include <Keypad.h>
const byte ROWS=4;
const byte COLS=4;
char keymap[ROWS][COLS]={
                          {'1','2','3','A'},
                          {'4','5','6','B'},
                          {'7','8','9','C'},
                          {'*','0','#','D'},

                      };

 byte rPin[ROWS]={13,12,11,10};
 byte cPin[COLS]={9,8,7,6,};

 Keypad myKeypad=Keypad(makeKeymap(keymap),rPin,cPin,ROWS,COLS);

 

void setup() {
  Serial.begin(9600);

}

void loop() {
 
 char key=myKeypad.getKey();

 if(key!=NO_KEY){
  Serial.print(key);
 }

}