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;
int N;
int recurseSum(int idx) {
  if (idx == 0) {
    return 0;
  }
  int sum = idx + recurseSum(idx - 1);
  return sum;
}
int main() {
  cin >> N;
  if (N == 1) {
    cout << 1 << endl;
    return 0;
  }
  vector<int> PS;
  vector<int> PS2;
  int acc = 0;
  for (int i = 1; i <= N; i++) {
    acc = recurseSum(i);
    PS.push_back(acc);
  }
  for (int i = 0; i <= N; i++) {
    if (i != 0) {
      PS2.push_back(PS[i] + PS2[i - 1]);
    } else {
      PS2.push_back(1);
    }
  }
  for (int i = 0; i < N; i++) {
    if (PS2[i] > N) {
      cout << i << endl;
      return 0;
    }
  }
  int ans = 0;
  return 0;
}
