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>
#pragma comment(linker, "/STACK:36777216")
using namespace std;
inline long long MAX(long long a, long long b) { return (a > b) ? (a) : (b); }
inline long long MIN(long long a, long long b) { return (a < b) ? (a) : (b); }
int const sz = 5e3 + 10;
long long hash1[sz + 1], hash2[sz + 1], po[sz + 1];
long long mod = 1e9 + 7, p = 137, l;
int main() {
  long long i, j, q, k, y, n;
  cin >> n;
  long long sum = 0;
  for (i = 1; i <= n + 10000; i++) {
    if (sum + i * (i + 1) / 2 > n) {
      cout << i - 1;
      return 0;
    }
    sum += i * (i + 1) / 2;
  }
  return 0;
}
