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


}