import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        boolean e=true;
        double a;

        do {
            try{
                e=false;
                Scanner scan = new Scanner(System.in);
                String xd = scan.nextLine();
                a = Double.parseDouble(xd);


            }
            catch(NumberFormatException ee){
                System.err.println("Zły typ gościu");
                e=true;

            }
        }
        while(e==true);
    }
}