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 gcd(int a, int b) {
  return (b > a) ? gcd(b, a) : (b == 0) ? a : gcd(b, a % b);
}
int bitcount(int a) { return (a != 0) ? bitcount(a & (a - 1)) + 1 : 0; }
long long bigmod(long long num, long long pow, long long prime) {
  if (pow == 0ll) return 1ll;
  long long ans = bigmod(num, pow / 2ll, prime);
  ans = (ans * ans) % prime;
  if (pow % 2ll) ans = (ans * num) % prime;
  return ans;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, now = 0, sum = 0, lvl = 0;
  cin >> n;
  for (int i = 1;; i++) {
    now += i;
    sum += now;
    if (sum <= n)
      lvl++;
    else
      break;
  }
  cout << lvl << endl;
  return 0;
}
