#include <Keypad.h>

const byte ROWS = 4;
const byte COLS = 4;

char hexaKeys[ROWS][COLS]={
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

byte rowPins[ROWS] = {3,4,5,6};
byte colPins[COLS] = {7,8,9,10};

Keypad customKeypad= Keypad(makeKeymap(hexaKeys),rowPins,colPins,ROWS,COLS);

char customKey;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  customKey = customKeypad.getKey();
  if(customKey != NO_KEY)
    Serial.println(customKey);
}