class GfG
{
    static final char MARKER = '$';
    static Set<String> subtrees = new HashSet<String>();
    public static boolean dupSub(Node root)
    {
        subtrees.clear();

        String res = dupSubUtil(root);
        if(res.compareTo("") == 0)
        return true;
        else
        return false;
    }

    public static String dupSubUtil(Node root)
    {
        String s = "";

        if(root == null)
         return s + MARKER;

        String lStr = dupSubUtil(root.left);
        if (lStr.compareTo(s) == 0)
            return s;

        String rStr = dupSubUtil(root.right);
        if (rStr.compareTo(s) == 0)
           return s;

        s = s + root.data + lStr + rStr;

         if (s.length() > 3 && subtrees.contains(s) == true)
                return "";

        subtrees.add(s);

        return s;
    }
}