#include <bits/stdc++.h> using namespace std; int main() { int n; while(cin>>n && n != 0) { int ge = 0; while(n >= 3) { ge += n / 3; int temp = (n / 3) + n % 3; n = temp; } if(n == 2) { ge++; } cout<<ge<<endl; } return 0; }