#include <iostream>

using namespace std;

int main() {
    int g;
    int x = 0;
    int gg_town=1;
    int b = 1;
    cin >> g;
    while (x != 1) {
        if(g<= gg_town)
        {
            cout << b;
            x=1;
        }
        gg_town = gg_town + (6*b);
        b++;
    }

    return 0;
}