import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        System.out.println("Square root!");
        double num;
        do{
            System.out.println("Enter a number(enter zero to exit): ");
            num = keyboard.nextInt();
           if (num <0){
               System.out.println("You can't take the square root of a negative number.");
               System.out.println("Enter a number (enter zero to exit): ");
               num = keyboard.nextInt();
           }else{
               System.out.println(Math.sqrt(num));
           }
       }while (num >= 0);

        System.out.println("Program closing");





    }
}