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>
def compare(element_a, element_b):
    if element_a > element_b:
        return True
    else:
        return False


def search_one_by_one(number_list, target):
    length = len(number_list)
    for index in range(length):
        if compare(number_list[index], target):
            return index
    else:
        return length


BEGIN_N = 1
END_N   = 10001

cubes_cnt_current_level = 0
cubes_cnt_sum = [cubes_cnt_current_level, ]
for level in range(BEGIN_N, END_N):
    cubes_cnt_current_level += level
    cubes_cnt_sum.append(cubes_cnt_sum[-1] + cubes_cnt_current_level)
    if (cubes_cnt_sum[-1] >= END_N):
        break

n     = input()
index = search_one_by_one(cubes_cnt_sum, n)
print index - 1