#include <iostream>
using namespace std;

int main() {
    int n;
    int sum = 1, pre = 1, cur;
    cin >> n;
    int i = 2;
    while (1) {
        cur = pre * i;
        sum += cur;
        if (sum >= n) break;
        i++;
        pre = cur;
    }
    cout << i - 1 << endl;
    return 0;
}