题解 | #汽水瓶#

import java.util.Scanner;

public class Main {
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            
            if(n == 0)break;
            // 数学问题 递归
            System.out.println(calc(n));
        }
    }
    // 每次喝到 n/3瓶 剩下n/3 + n%3个空瓶
    static int calc(int n){
        if(n < 2)return 0;
        if(n == 2)return 1;
        // 喝到
        int ret = n/3 + calc(n/3 + n%3);
        return ret;
        
    }
}