public class Tree {
    private static String tree = "tree";

    String getTree() {
        return tree;
    }

    public static class Elm extends Tree {
        private static String tree = "elm";

        public static void main(String[] args) {
            new Elm().go(new Tree());
        }

        void go(Tree t) {
            String s = t.getTree() + Elm.tree + tree + (new Elm().getTree());
            System.out.println(s);
        }
    }
}