Leetcode: Sqrt(x) @Python

class Solution:
    # @param x, an integer
    # @return an integer
    def sqrt(self, x):
        a=1000.0#guess
        new_a=(a*1.0+x/a)/2
        while int(new_a)!=int(a):
            a=new_a
            new_a=(a*1.0+x/a)/2
        return int(a)