import java.util.Scanner;

/**
   This program shows how you can prompt for input that fulfills
   a certain condition. Try entering negative values, such as
   -2 or -0.5, to see how they are rejected.
*/
public class DoLoop 
{
   public static void main(String[] args)
   {
      Scanner in = new Scanner(System.in);
      
      double value;
      do
      {
         System.out.print("Enter a number >= 0: ");
         value = in.nextDouble();
      }
      while (value < 0);
      double root = Math.sqrt(value);
      System.out.println("The square root of the number is " + root);
   }
}

