c = int(input())
now = 0
N = 1000
while 1:
    nxt = now + 1
    t = nxt * nxt * nxt * nxt * nxt + nxt * N * N * N * N - c * N * N * N * N * N
    if t <= 0:
        now = nxt
    else:
        break

print(now / 1000)