Codeforces 492A. Vanya and Cubes 水



A. Vanya and Cubes
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

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.

Sample test(s)
input
1
output
1
input
25
output
4
Note

Illustration to the second sample:

Codeforces 492A. Vanya and Cubes 水_第1张图片


__author__ = 'ckboss'

n = int(raw_input())

sum = 0
ans = 0

for i in range(0,100):
    sum += (i+1)*i/2
    if sum > n:
        break
    else :
        ans = i

print ans


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