#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n;
    cin >> n;
    int c = 0;
    while(n!=0){
        if(n-3>=2 || n-3 == 0){
            n = n-3;
            c++;
        }else{
           n = n-2;
           c++;
        }
    }
    cout << c;
}