Vanya got n cubes. He decided to build a pyramid from them. Vanya wants to build the pyramid as follows: the top level of the pyramid must consist of 1 cube, the second level must consist of 1 + 2 = 3 cubes, the third level must have 1 + 2 + 3 = 6 cubes, and so on. Thus, the i-th level of the pyramid must have 1 + 2 + ... + (i - 1) + i cubes.

Vanya wants to know what is the maximum height of the pyramid that he can make using the given cubes.

Input

The first line contains integer n (1 ≤ n ≤ 104) — the number of cubes given to Vanya.

Output

Print the maximum possible height of the pyramid in the single line.

Examples

Input

1


Output

1


Input

25


Output

4

Note

Illustration to the second sample: 

<image>
#include <bits/stdc++.h>
using namespace std;
void printarray(int arr[], int n) {
  for (int i = 0; i < n; i++) cout << arr[i] << " ";
  cout << "\n";
}
int isprime(int a) {
  int t = 0;
  if (a == 2 || a == 3) return 1;
  for (int i = 2; i <= a / 2; i++) {
    if (a % i == 0) return 0;
  }
  return 1;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cerr.tie(0);
  int n;
  cin >> n;
  if (n < 4) {
    cout << 1;
    return 0;
  }
  int d = 2, c = 1;
  n = n - 1;
  for (int i = 2; i < n; i++) {
    c = c + i;
    if (c == n) {
      cout << d;
      return 0;
    }
    n = n - c;
    if (n < (c + i + 1)) {
      cout << d;
      return 0;
    }
    d++;
  }
  return 0;
}
