一开始low和high的取值考虑到a比设为（-1,1）后面分类和a比较要更简洁

a = float(input())
low = min(-1, a)
high = max(1,a)
ans = (low + high) / 2
e = 0.00001
while abs(ans ** 3 - a) > e: #只有两个情况，小了右移，大了左移，更新low，high
    if ans**3 < a:
        low = ans
    else:
        high = ans
    ans = (high + low) / 2 #更新ans
print(format(ans,'.1f'))