题解 | #汽水瓶#

#include <iostream>
using namespace std;

int main() {
    int n;
    while (cin >> n) { // 注意 while 处理多个 case
        if(n == 0) break;
        int one = 0, countB = n;
        while (true) {
            if(countB >= 3){
                one += countB /3;
                countB = countB%3 + countB/3;
            }else if(countB >=2){
                // 借一个空瓶
                countB += 1;
                one += countB/3;
                countB = countB%3 + countB/3;
                countB -= 1;// 还一个空瓶
            }else if(countB < 2){
                break;
            }
        }
        cout << one << endl;
    }
}
// 64 位输出请用 printf("%lld")