#include<bits/stdc++.h> using namespace std; int main(){ int num; vector<int>ret; while(cin>>num){ if(num==0) break; int sum=0; while(num>2) { sum+=num/3; num=num/3+num%3; } if(num==2) sum+=1; ret.push_back(sum); } for(int i=0;i<ret.size();i++) cout<<ret[i]<<endl; return 0; }