题解 | #求解立方根#

from operator import le
n = float(input())
if n<0:
    flag = -1
elif n>0:
    flag = 1
else:
    flag = 0

if flag == 0:
    print(0.0)
else:
    n = abs(n)  #abs=absolute()，取绝对值
    # 用二分法处理
    if n>=1:
        left = 1
        right = n
    else:
        left = n
        right = 1
    mid = (left + right)/2

    while abs(mid**3-n) >0.001:
        if mid**3>n:
            right = mid
        else:
            left = mid
        mid = (right + left)/2
    print(round(mid*flag,1))