#include<bits/stdc++.h>
#define ll long long
#define endl '\n'

using namespace std;

int32_t main() {
    ios_base :: sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    int n;
    cin >> n;


    int ansmod3 = n % 3;

    if (ansmod3 == 1) {
        cout << (n / 3) + 1 << endl;
    }
    else if (ansmod3 == 2) {
        cout << (n / 3) + 1 << endl;
    }
    else {
        cout << (n / 3) << endl;
    }

    return 0;
}