num = float(input())
if num < 0:
    sign = -1
    num = -num
else:
    sign = 1
l = 0
r = 1 if 0 < num < 1 else num
while (r - l > 0.0001):
    m = (r + l) / 2
    if (m**3) < num:
        l = m
    else:
        r = m
print(round(sign*m, 1))