"""
[25373: 벼락치기](https://www.acmicpc.net/problem/25373)
Tier: Bronze ??
Category: 구현
"""
def solution():
n = int(input())
s = 1
e = 100000000000000000
ans = e
while s <= e:
mid = (s + e) // 2
t = sum([max(i, 0) for i in range(mid, mid - 7, -1)])
if n > t:
s = mid + 1
else:
ans = min(ans, mid)
e = mid - 1
return ans
if __name__ == '__main__':
print(solution())