class WrongNumberException extends Exception { 
    private int num;
    WrongNumberException(int num) {
        this.num = num;
    }
    @Override
    public String toString() {
        String msg;
        if (num == 0) {
            msg = "Error! Zero number!";
        }else if(num < 0) {
            msg = "Error! Negative number!";
        }else {
            msg = "Error! Other error!";
        }
        return msg;
    }
}
 
class App {
    static int kerSzam() {
        return -9;
    }
 
    public static void main(String args[]) throws Exception {
        int szam = kerSzam();
 
        if(szam<=0)
            throw new WrongNumberException(szam);
        else
            System.out.println("A szam: " + szam);
    }
}