#include<Keypad.h>

const byte ROW_NUM=4;                //four  rows
const byte COLUMN_NUM=4;             //four  columns 

char keys[ROW_NUM][COLUMN_NUM]{
  {'1','2','3','A'},
    {'4','5','6','B'},
      {'7','8','9','C'},
        {'*','0','#','D'}

        };

        byte pinRow[ROW_NUM]={9,8,7,6};
        byte pinColumn[COLUMN_NUM]={5,4,3,2};

        Keypad keypad=Keypad (makeKeymap(keys),pinRow,pinColumn,ROW_NUM,COLUMN_NUM);

        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){
          Serial.println(key);
          }
          }