import java.util.*;

class N {
    Object box = null;
}

class Main {

    static void A(int k, String te) {
        if (k > 0) {
            System.out.println(te);
            A(k - 1, te);
        }
    }

    public static void main(String[] args) {

        N a = new N();
        N e = a;

        e.box = "Hello world!";

        String tt = (String)a.box;

        A(15, tt);
    }
}