#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);
const int butup = 3;
const int butdown = 2;
bool up;
bool down;
byte absen;

void setup(){
  pinMode( butup, INPUT_PULLUP);
  pinMode( butdown, INPUT_PULLUP);
  lcd.init();
  lcd.backlight();
  Serial.begin(9600);
}

void loop(){
  up = digitalRead(butup);
  down = digitalRead(butdown);
  if (up == 0){
    if (absen == 23){
      absen++;
    }
    else {
      absen = absen+1;
    }
    while(up == 0){
      up = digitalRead(butup);
      if (up == 1) break;
    }
  }
  if (down == 0){
    if(absen == 0){
      absen-0;
    }
    else{
      absen--;
    }
    while(down == 0){
      down = digitalRead(butdown);
      if (down == 1) break;
    }
  }
  lcd.setCursor(0, 0);
  lcd.print("Nomor Urut : ");
  lcd.print(absen);
  lcd.print("  ");
  Serial.println(absen);
}