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

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

    if(n==2 || n==3){
        cout<<1<<endl;
    }
    else if(n%3==0){
        cout<<n/3<<endl;
    }
    else if(n%3==2){
        cout<<n/3+1<<endl;
    }
    else {
        cout<<n/3+1<<endl;
    }
}