Acwing 790 数的三次方根
https://www.acwing.com/activity/content/problem/content/824/1/
n = float(input()) def binarySearch(L, R): while R - L > 1e-8: mid = (L + R) / 2 if mid * mid * mid > n: R = mid else: L = mid return L if n > 0: res = binarySearch(0, n) else: res = binarySearch(n, 0) print('%.6f' % res)