#include <Keypad.h>
#include <LiquidCrystal.h>

// LCD pin setup
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

// Keypad setup
const byte ROWS = 4; // Four rows
const byte COLS = 4; // Four columns
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}; // Connect to the row pinouts of the keypad
byte colPins[COLS] = {5, 4, 3, 2}; // Connect to the column pinouts of the keypad
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

int num1 = 0;
int num2 = 0;
int sum = 0;
bool firstNumberEntered = false;

void setup() {
  lcd.begin(16, 2); // Initialize the LCD, 16 columns by 2 rows
  lcd.print("Enter 1st num:");
}

void loop() {
  char key = keypad.getKey(); // Get the key pressed

  if (key) { // If a key is pressed
    if (key >= '0' && key <= '9') { // If the key is a number
      lcd.print(key); // Display the key on the LCD

      if (!firstNumberEntered) {
        num1 = num1 * 10 + (key - '0'); // Store the first number
      } else {
        num2 = num2 * 10 + (key - '0'); // Store the second number
      }
    } else if (key == '#') { // '#' to enter the next number or calculate sum
      if (!firstNumberEntered) {
        firstNumberEntered = true; // Indicate the first number is entered
        lcd.setCursor(0, 1);
        lcd.print("Enter 2nd num:");
      } else {
        sum = num1 + num2; // Calculate sum
        lcd.clear();
        lcd.setCursor(0, 0); // Set cursor to the first row, first column
        lcd.print("Sum: ");  // Display "Sum: "
        lcd.print(sum);      // Display the sum
      }
    } else if (key == '*') { // '*' to reset
      num1 = 0;
      num2 = 0;
      sum = 0;
      firstNumberEntered = false;
      lcd.clear();
      lcd.print("Enter 1st num:");
    }
  }
}