/*
 *Copyright (c) Swadheen Islam Robi (SIR01)
 *Created on Thu Oct 03 2024 8:21:05 PM
 */
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pie 2*(acos(0.0))
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define pb push_back
#define endl "\n"
#define lcm(a,b) (a*b)/(__gcd<ll>(a,b))
#define mod 1000000007
#define srt(v) sort(v.begin(),v.end())
#define rsrt(v) sort(v.rbegin(),v.rend())
#define ALLAHU_AKBAR ios::sync_with_stdio(false); cin.tie(nullptr);

void sir()
{
    // int y
    int n;cin>>n;
    int ans=0;
    if(n<=3) cout<<1<<endl;
    else if(n%3==0) cout<<n/3<<endl;
    else if((n-2)%3==0) cout<< 1 + (n-2)/3<<endl;
    else{
        while(n)
        {
            n-=3; ans++;
            if(n%2==0) {
                ans += n/2;break;}
        }
        cout<<ans<<endl;
    

    }
}

int main() {
    ALLAHU_AKBAR

    ll t = 1;
    //cin>>t;
    while(t--)
    {
        sir();
    }
    return 0;
}