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>
import sys

local_launch = False
try:
    open('LOCAL').read()
    local_launch = True
except:
    pass

input_data = open('INPUT.txt').read() if local_launch else sys.stdin.read()
done = {'i': 0}
tokens = input_data.split()

def next_token():
    result = tokens[done['i']]
    done['i'] += 1
    return result

def next_int():
    return int(next_token())

def next_str():
    return next_token()

############## BEGIN OF CODE #####################
n = next_int()
s = n
i = 1
def level(i):
    a = 0
    b = 1
    while b <= i:
        a = a+ b
        b = b+ 1
    return a
while level(i)<= s:
    s -= level(i)
    i += 1
print(i-1)






