#include <Keypad.h>

const int ROW_NUM = 4; //four rows
const int COLUMN_NUM = 4; //three columns
String password = "1234";
String inputPass;
char keys[ROW_NUM][COLUMN_NUM] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

byte pin_column[COLUMN_NUM] = {22,24, 26, 28}; //connect to the row pinouts of the keypad
byte pin_rows[ROW_NUM] = {30, 32,34,36}; //connect to the column pinouts of the keypad

Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );

void setup(){
  Serial.begin(9600);
  pinMode(25, OUTPUT);
  digitalWrite(25, HIGH);
}

void loop(){
  char key = keypad.getKey();

  if (key){
    
    inputPass = inputPass + key;
    if(inputPass.length()==4){
      if(inputPass == password){
        Serial.println("Welcome!");
        digitalWrite(25, LOW);
        delay(3000);
        digitalWrite(25,HIGH);
      }
      else{
        Serial.println("Incorrect!");
        delay(3000);
      }
      inputPass = "";
    }
    Serial.println(inputPass);
    
  }
}