题解 | #汽水瓶#

#include<bits/stdc++.h>
using namespace std;

int main() {
    int n;
    int empty = 0;
    
    while (cin >> n) {
        int sum = 0;
        
        while (n > 2) {
            
            empty = n / 3;
            sum += empty;
            n = n % 3 + empty;
        }
        if (n == 0) {
            
            return 0;
        }
//         cout << 'a' << n << endl;
        sum += n - 1;
        cout << sum << endl;
    }
}