#include <Keypad.h>
const uint8_t ROWS=4;
const uint8_t COLS=4;
char keys [ROWS][COLS]={
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
uint8_t colPins[COLS]={5,4,3,2};
uint8_t rowPins[ROWS]={9,8,7,6};
Keypad keypad=Keypad(makeKeymap(keys),rowPins,colPins,ROWS,COLS);

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

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