#define set0(r,b) r &= ~(1<<b)
#define set1(r,b) r |= 1<<b
#define test(r,b) (r&(1<<b))

int cislo = 0;
int cislo2 = 0;

#include <LiquidCrystal_I2C.h>

#define I2C_ADDR    0x27
#define LCD_COLUMNS 16
#define LCD_LINES   2

LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);

void setup() {
  lcd.init();
  lcd.backlight();
  set0(DDRD, 3);
  set1(PORTD, 3);
  set1(EIMSK, 1);
  set1(SREG, 7);
  set1(EICRA, ISC11);
  set0(EICRA, ISC10);
}

void loop() {

  if(cislo2 != cislo){
    lcd.clear();
    lcd.print(cislo);
    cislo2 = cislo;
  }

}

ISR(INT1_vect){
  cislo += 1;
}