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>
from __future__ import division
from collections import Counter as ctr
import math
def rl():
	return [int(i) for i in raw_input().split()]

def rm(n=None):
	if n is None:
		n = input()
	return [raw_input() for i in range(n)]

def rlm(n=None):
	if n is None:
		n = input()
	return [rl() for i in range(n)]

def yn(b):
	if b:
		print "YES"
	else:
		print "NO"

n = input()
i = 1
while True:
	n = n - i*(i+1)//2
	i += 1
	if n < 0:
		break
print i - 2