private File process(ArrayList<File> list) throws IOException {
        if (list.size() == 1) {
            return list.get(0);
        }
        ArrayList<File> inter = new ArrayList<File>();
        for (Iterator<File> itr = list.iterator(); itr.hasNext();) {
            File one = itr.next();
            if (itr.hasNext()) {
                File two = itr.next();
                inter.add(merge(one, two));
            } else {
              //  return one;
            	inter.add(one);
            }
        }
        return process(inter);
    }