#include<bits/stdc++.h>
using namespace std;
int s;
int main() {
    int n,t;
    cin>>n;
    while(n>=3) {
        s+=n-n%3;
        n=n/3+n%3;
    }
    cout<<s+n;
    return 0;
}

为什么样例对了但全WA呢