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;
template <typename T>
inline T maxer(T &a, T b) {
  a = max(a, b);
}
template <typename T>
inline T miner(T &a, T b) {
  a = min(a, b);
}
void iOS() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
}
void fin() { freopen("in", "r", stdin); }
void fout() { freopen("out", "w", stdout); }
const int inf = ~0u / 10;
const long long linf = ~0ull / 2;
const int maxn = 1e5 + 20;
;
int main() {
  iOS();
  long long cur = 0, i = 1;
  int n;
  cin >> n;
  while (cur <= n) cur += (i * (i + 1)) / 2, i++;
  cout << i - 2;
  return 0;
}
