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>
'''
492a
n cubes given to Vanya
print: height of pyramid that can be made where
top layer has 1,
next 1+2
next 1+2+3
etc. cubes
'''

#~ import io
#~ import sys
#~ test = '''1'''
test = '''25'''
#~ sys.stdin = io.StringIO(test)


n, = map(int, input().split() )
l = 1
cubes_in_layer = 1
while n>=cubes_in_layer:
   n -= cubes_in_layer
   l += 1
   cubes_in_layer += l

print(l-1)
