public void run() {
        while (true) {
            int from = randomFloor();
            int to = randomFloor();

            while (from == to) {
                to = randomFloor();
            }

            try { Thread.sleep((int) (46000 * Math.random())); }
            catch (InterruptedException e) { e.printStackTrace(); }

            monitor.call(from, to);
        }
    }