难点在于保留限定小数点,如果用round会出现1.99999999进位=2.0无法保留要求的小数点
N = float(input())
def function(n):
left = -10001
right = 10001
while abs(left - right) > 1E-8:
mid = (left + right) / 2
if mid**3 < n:
left = mid
else:
right = mid
print('%.6f' %left)
function(N)