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;
const int mod = 1000000007;
int ADD(int a, int b) { return a + b >= mod ? a + b - mod : a + b; }
int SUB(int a, int b) { return a - b < 0 ? a - b + mod : a - b; }
int MUL(long long a, long long b) { return a * b % mod; }
double beginTime;
int dx[] = {0, 1, 0, -1};
int dy[] = {+1, 0, -1, 0};
bool Can(int k, int n) {
  int r = 0, t = 0;
  for (int i = (1), _b(k + 1); i < _b; ++i) {
    t += i;
    r += t;
    if (r > n) return false;
  }
  return true;
}
int main() {
  int n;
  cin >> n;
  for (int i = (1), _b(n + 2); i < _b; ++i) {
    if (!Can(i, n)) {
      cout << (i - 1) << endl;
      break;
    }
  }
  return 0;
}
