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

#define ROWS 4
#define COLS 4

char keys[ROWS][COLS] = {
  { '1', '2', '3', '+' },
  { '4', '5', '6', '-' },
  { '7', '8', '9', '*' },
  { '^', '0', '=', '/' }
}

keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);
LiquidCrystal_I2C lcd(0x27, 20, 4);

void setup()
{
  lcd.begin(20, 4);
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0, 0);
}

void loop()
{

}