val = float(input())

neg_flag = val < 0
val = abs(val)

l, r = 0.0, 10001
while abs(l-r) >= 1e-8:
    mid = l + (r-l) / 2
    if mid**3 < val:
        l = mid
    else:
        r = mid

ans = l if not neg_flag else -l
print('{:.6f}'.format(ans))