#include <Key.h>
#include <Keypad.h>
const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
char hexaKeys[ROWS][COLS] = {
{'1','2','3','A'}, {'4','5','6', 'B'}, {'7','8','9', 'C'}, {'*','0','#','D'}
};
byte rowPins[ROWS] = {10, 9 ,8,7}; 
byte colPins[COLS] = {6,5,4,3 }; //byte rowPins[ROWS] = {3, 4 , 5, 6};  byte colPins[COLS] = {7, 8, 9, 10 }; 
Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);
void setup(){
Serial.begin(9600);
}
void loop(){
char customKey = customKeypad.getKey();
if (customKey){ 
Serial.println(customKey);
}
}