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>
'''
Created on Apr 21, 2016
Gmail : r.haque.249.rh@gmail.com
@author: Md. Rezwanul Haque
'''
n = int(input())
#s = 0
i = 1
'''while(n):
    s = s + k
    n = n - s
    if n - (s + k)<=0:
        break
    k = k+1
    #print(k)
print(k)'''
while (i*(i+1)*(i+2)/6 <= n):
    i = i+1  
print(i-1)
