#include <LiquidCrystal_I2C.h>
const int countUp = 3;
const int countDown = 2;
const int maxPerson = 15;

LiquidCrystal_I2C lcd(0x27, 16, 2);

int minPerson = 0;
int interval= 0;

void setup() {
  pinMode(countUp, INPUT);     
  pinMode(countDown, INPUT);   
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Starting count...");
  delay(3000);
  lcd.clear();
}

void loop(){
  if (digitalRead(countUp) == 1 && interval < maxPerson){
    interval += 1;
    lcd.clear();
    delay(200);
  }
  if (digitalRead(countDown) == 1 && interval > minPerson){
    interval -= 1;
    lcd.clear();
    delay(200);
  }
  lcd.setCursor(0, 0);
  lcd.print("Person : ");
  lcd.print(interval);
}