# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	ans = int((N / 6) ** 0.5 // 1)
	print(max(ans, 1))


if __name__ == '__main__':
	main()