题解 | #汽水瓶#

#include <iostream>
using namespace std;

int main() {
    int a;
    while (cin >> a) {
        if (a == 0) {
            break;
        }
        int res = 0;
        while (a > 2) {
            int temp = a / 3;
            res += temp;
            a = a % 3 + temp;
        }
        if (a == 2) {
            res += 1;
        }
        cout << res << endl;
    }
    return 0;
}