#include<bits/stdc++.h>
using namespace std;
#define optimize() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl '\n'
#define ll long long int
int main()
{
    optimize();
    int n;
    cin >> n;
    cout<<min((n/2),(n/3))<<endl;
 }