private List<String> getInterConnected(List<List<String>> connectedLines1,
            List<List<String>> connectedLines2) {
        for (List<String> line1 : connectedLines1) {
            for (List<String> line2 : connectedLines2) {
                List<String> line = intersection(line1, line2);
                if (!line.isEmpty()) {
                    return line;
                }
            }
        }
        return null;
    }