#include <Wire.h>
#include <Key.h>
#include <Keypad.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);
const byte ROWS = 4; 
const byte COLS = 4; 

char hexaKeys[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};

char pass[4] = {'1', '2', '3', '4'};
char buttons[5]; 
int k = 0;

Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);

void setup() {
      Serial.begin(9600);
      lcd.init(); 
      lcd.backlight();
}

void loop() {
      lcd.setCursor(0, 0); 
      lcd.print("Enter password!");
      lcd.setCursor(0, 1); 
      char customKey = customKeypad.getKey();
      if (customKey) {
            buttons[k] = customKey; 
            lcd.setCursor(k, 1);
            lcd.print('*');
            k = k + 1; 
            if (k == 4) { 
                  if (buttons[0] == pass[0] && buttons[1] == pass[1] && buttons[2] == pass[2] && buttons[3] == pass[3])
                  { 
                    lcd.clear();
                    lcd.setCursor(0, 1);
                    lcd.print("Access granted!"); 
                  }
            else {
                    lcd.clear();
                    lcd.setCursor(0, 1);
                    lcd.print("Access denied!");
                  }
            }
      }
}