import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n = ii()
sm = 0
cnt = 0
while 1:
z = (cnt + 1) ** 2
if sm + z <= n:
sm += z
cnt += 1
else:
break
print(cnt)
if __name__ == "__main__":
tc = 1
for t in range(tc):
solve()