#include<bits/stdc++.h> using namespace std; int main(){ int a,b,n=1,c,d; while(n==0){ d=0; cin>>n; c=n+1; if(n<3){ cout<<'0'<<endl; }else{ while(c>=3){ a=c%3; b=c/3; d=d+b; c=b+a; } cout<<d<<endl; } } }