题解 | #汽水瓶#

#include <iostream>
using namespace std;

int bottle_n(int n){
    if (n == 1){
        return 0;
    }
    else if (n == 2){
        return 1;
    }else return n/3 + bottle_n(n/3 + n % 3);
}

int main() {
    int n;
    while (cin >> n) {
        if (n == 0)
            break;
        else cout << bottle_n(n) <<endl; 
    }
    return 0;
}