#include <bits/stdc++.h>
using namespace std;
bool compare(const int &a, const int &b) { return a < b; }
int main() {
  int n;
  cin >> n;
  int i = 0;
  double aux = 0;
  while (n >= aux) {
    aux = (1.0 / 6.0) * (i) * (i + 1) * (i + 2);
    i++;
  }
  cout << i - 2 << endl;
  return 0;
}
