#include<bits/stdc++.h>

using namespace std;

#define ll long long
#define all(a) a.begin(),a.end()
#define endl '\n'

int main()
{
    ios::sync_with_stdio(0); cin.tie(0);
   ll n;cin>>n;
   ll ct=0;
   while(n){
    if(n-3!=1)n-=3;
    else n-=2;
    ct++;
   }
   cout<<ct<<endl;
        
}