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>
"""====================================================================================
   ====================================================================================
   
    ___             _______  ___    _______       ___   ___
   |         /\        |    |   \      |    |  / |   | |   | |\    /|
   |        /  \       |    |    \     |    | /  |   | |   | | \  / |
   |___    /____\      |    |     \    |    |/   |___| |   | |  \/  |
       |  /      \     |    |     /    |    |\   |\    |   | |      |
       | /        \    |    |    /     |    | \  | \   |   | |      |
    ___|/          \___|___ |___/   ___|___ |  \ |  \  |___| |      |
 
       
   ====================================================================================
   ==================================================================================== 
"""
# ♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥

h,ans = 0,0
n = int(input())
while ans <= n:
    h += 1
    ans += (h*(h+1))//2
print(h-1)
exit()

# ♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥
"""====================================================================================
   ====================================================================================
   
    ___             _______  ___    _______       ___   ___
   |         /\        |    |   \      |    |  / |   | |   | |\    /|
   |        /  \       |    |    \     |    | /  |   | |   | | \  / |
   |___    /____\      |    |     \    |    |/   |___| |   | |  \/  |
       |  /      \     |    |     /    |    |\   |\    |   | |      |
       | /        \    |    |    /     |    | \  | \   |   | |      |
    ___|/          \___|___ |___/   ___|___ |  \ |  \  |___| |      |
 
       
   ====================================================================================
   ==================================================================================== 
"""
