#include<bits/stdc++.h> using namespace std; int main(){ int n; for(int i=1;i<=100;i++){ int sum=0,shengyu=0; cin>>n; if(n==0) break; while(n>2){ sum=sum+n/3; shengyu=n/3; n=n%3; n+=shengyu; } if(n==2) sum++; cout<<sum<<endl; } }