public String contract(String[] words) {
        String ret = null;

        if (words.length == 2) {
            if (words[1].equals("el")) {
                if (words[0].equals("a")) {
                    ret = "al";
                } else if (words[0].equals("de")) {
                    ret = "del";
                }
            }
        }

        return ret;
    }