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

int main()
{
    int N;
    cin>>N;

    int Ans=N/3;

    if (N%3 != 0)
    {
        Ans+=1;
    }
    cout<<Ans<<endl;

    return 0;
}