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>
#!/usr/bin/env python3
"""
CodeForces
492 A. Vanya and Cubes

@author yamaton
@date 2015-07-29
"""
import itertools


def solve(n):
    def f(x):
        return x * (x + 1) * (x + 2) // 6

    out = itertools.takewhile(lambda i: i <= n, map(f, itertools.count(1)))
    return sum(1 for _ in out)


def test():
    assert solve(1) == 1
    assert solve(25) == 4


def main():
    n = int(input())
    result = solve(n)
    print(result)


if __name__ == '__main__':
    main()
