백준 2292번 벌집

# 1 -> 6 -> 12 -> 18 -> 24

# 1 (1+0*6) --> 1개
# 2~7(1+1*6) --> 2개
# 8~19(7+2*6) --> 3개
# cnt+1 ~ cnt + flg*6 --> flg+1개

N = int(input())

cnt = 1
flg = 0

while N > cnt :
    flg += 1
    cnt += flg*6

print(flg+1)