题解 | #汽水瓶#

import java.util.Scanner;
public class Main {
    public static int fun(int n, int num) {
        num = num + n / 3;
        if (n == 2) {
            num = num + 1;
            n = 0;
        } else {
            n = n % 3 + n / 3;
        }
        if (n != 0 && n != 1) {
            num = fun(n, num);
        } else if (n == 1) {
            n = 0;
        }
        return num;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int n = sc.nextInt();
            if (n > 1) {
                System.out.println(fun(n, 0));
            } else if (n == 1) {
                System.out.println(1);
            } else {
                break;
            }
        }
    }
}