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

LiquidCrystal_I2C lcd(0x27, 16, 2);
const int C = 4;
const int R = 4;
char keys[R][C] = {
  {'1', '2', '3', '+'},
  {'4', '5','6','-'}, 
  {'7','8','9','x'},
  {'.', '0', '=', '/'}
};

byte rpins[R] = {13, 12, 11, 10};
byte cpins[C] = {9, 8, 7, 6};

Keypad keypad = Keypad(makeKeymap(keys), rpins, cpins, R, C);

void setup()
{
  // put your setup code here, to run once:
  lcd.init();
  lcd.backlight();
}

void loop()
{
  // put your main code here, to run repeatedly:
  lcd.setCursor(0,0);
  char key = keypad.getKey();
  
  if (key)
    lcd.print(key);
}