using System;

class Square_Root
{
    static void Main(string[] args)
    {
        double a,root;
	  	do
	  	{
                Console.Write("Enter a number: ");
	    		a=Convert.ToDouble(Console.ReadLine());
	    		if (a<0)
	      		    Console.WriteLine("Please enter a positive number!");
	  	} while (a<0);
	  	root=a/2;
	  	double root_old;
	  	do
	  	{
	    		root_old=root;
	    		root=(root_old+a/root_old)/2;
	  	} while (Math.Abs(root_old-root)>1.0E-6);

	  	Console.WriteLine("The square root of " + a + " is " + root);
    }
}