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>
#!/usr/bin/env python
#-*- coding:utf-8 -*-

import sys
import math
import random
import operator
from fractions import Fraction, gcd
from decimal import Decimal, getcontext
from itertools import product, permutations, combinations
getcontext().prec = 100

MOD = 10**9 + 7
INF = float("+inf")

n = int(raw_input())

a = 1
s1 = 0
s2 = 0
while 1:
    s1 += a
    s2 += s1
    #print a, s1, s2
    if s2 <= n:
        a += 1
    else:
        print a - 1
        break


