#include<bits/stdc++.h> using namespace std; int n,left1,ans; int main(){ while(1){ cin>>n; if(n==0) break; ans=0; left1=n; while(left1>=2){ ans+=left1/3; left1=ans+n-ans*3; if(left1==2) ans++; } cout<<ans<<endl; } return 0; }