#include <Keypad.h>
const byte ROWS = 4;
const byte COLS = 4;
char keys [ROWS] [COLS] = {
{'1','2','3','A'},
{'4','5','6','B'},
{'7','8','9','C'},
{'*','0','#','D'}
};
byte rowPins[ROWS] ={9, 8, 7, 6 };
byte colPins[COLS] ={5, 4, 3, 2 };
Keypad keypad = Keypad ( makeKeymap (keys),rowPins,colPins,ROWS,COLS);
void setup() {
  Serial.begin(9600);
}
void loop() {
char key = keypad.getKey();
if (key)
{
Serial.print(key);
}

}