2292

import sys

sys.stdin = open("input.txt","rt")

a = int(sys.stdin.readline().strip())

x = 1
cnt = 1


for i in range(1, a):

    if x < a <= x + (6*i):
        cnt += i
        break

    x += 6 * i


if a == 1:
    cnt = 1


print(cnt)