void main(String[] arguments) throws Exception {
    if (arguments.length != 2) {
        IO.println("Usage: java Mediator.java <from-mailbox> <to-mailbox>");
        return;
    }

    var from = arguments[0];
    var to = arguments[1];

    IO.println("Mediating: " + from + " -> " + to);

    FileMessageBoard.watch(from, message -> {
        try {
            FileMessageBoard.publish(to, message);
        } catch (IOException exception) {
            throw new UncheckedIOException(exception);
        }
    });
}