Root of number - binary search

RootOfNumber.cs

using System;

class Solution
{
    public static double Root(double x, int n)
    {
      // your code goes here
      double lower = 0;
      double upper = Math.Max(x, 1);
      
      while (lower <= upper)
      { 
        double mid = (lower + upper)/2;
        double curGuess = Math.Pow(mid, n);
                
        if (Math.Abs(curGuess - x) < 0.001)
        {
          return Math.Round(mid * 1000)/((double)1000);  // round up math.round 0.5 -> 1, 0.4 -> 0 , mid * 1000 
        }
        
        if (curGuess > x)
        {
          upper = mid;
        }
        else if (curGuess < x)
        {
          lower = mid;
        }
      }
      
      return -1;
    }

    static void Main(string[] args)
    {
      Console.WriteLine(Root(0.04, 2));    
    }
}
/*
x > 1, 
x >= x
x * x >= x
x * x * x >= x

*/