#include <Keypad.h>

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

  byte row_pins[4]={9,8,7,6};
  byte col_pins[4]={5,4,3,2};

  Keypad kp = Keypad(makeKeymap(key),row_pins,col_pins,4,4);
void setup() {
  Serial.begin(9600);

}

void loop() {
  char key = kp.getKey();
  if(key)
  {
    Serial.print(key);
  }
}