题解 | 汽水瓶

#include <iostream>
using namespace std;
int dh(int n){
    if(n<2)return 0;
    if(n==2)return 1;
    return n/3+dh(n%3+n/3);
}
int main() {
    int n;
    while(cin>>n){
        if(n==0)return 0;
        cout<<dh(n)<<endl;
    }
}