import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        String user;
        Scanner scanner = new Scanner(System.in);
        do {
            System.out.print("Student Number: ");
            user = scanner.nextLine();

            if(user.matches("[0-9]{4}-[0-9]{2}-[0-9]{3}"))
                break;

            System.out.println("Invalid student number.");
        } while(true);

        System.out.println("Your student number is " + user);
    }
}