写完才发现，瓶子数除以2就结束了？！！！淦

import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        while(sc.hasNext()){
            int num = sc.nextInt();
            if(num == 0) break;
            int count = 0;
            while(num >= 2){
                num -=2;
                count++;
            }
            System.out.println(count);
        }
    }
}