#include <iostream>
using namespace std;

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

    int min_operations = 1e9;

    for (int x = 0; x <= N / 3; x++) {
        int remaining = N - (x * 3);
        if (remaining % 2 == 0) {
            int y = remaining / 2;
            min_operations = min(min_operations, x + y);
        }
    }

    cout << min_operations << endl;
    return 0;
}