public class Main {
    public static void main(String[] args) {
        Train train = new Train(5000, 5000);

        Counter counter = new Counter(train);
        counter.countNumberOfCars();
    }
}

class Train {
    private boolean[] lightsInCar;
    private int size;
    private int currentCarIndex;
    private static Random random = new Random();

    Train(int minimalSize, int maximumSize) {
        size = minimalSize + (int) (Math.random() * (maximumSize - minimalSize + 1));

        lightsInCar = new boolean[size];

        for (int i = 0; i < size; i++) {
            lightsInCar[i] = random.nextBoolean();
        }
        currentCarIndex = 0;
    }

    void gotoNextCar() {
        currentCarIndex = (currentCarIndex + 1) % size;
    }

    void gotoPreviousCar() {
        currentCarIndex = (currentCarIndex + size - 1) % size;
    }

    boolean getLigtsStatusInCar() {
        return lightsInCar[currentCarIndex];
    }

    void setLigtsOnInCar(boolean status) {
        lightsInCar[currentCarIndex] = status;
    }
}

class Counter {
    private Train train;
    private int minimalNumberOfCars;

    Counter(Train train) {
        this.train = train;
    }

    void countNumberOfCars() {
        int guess = guessNumberOfCars();

        System.out.println("Number of cars where should stop: " + guess);

        int i = 0;

        while (true) {

            i++;

            if (i == guess) {
                train.setLigtsOnInCar(true);
                break;
            } else {
                train.setLigtsOnInCar(false);
                train.gotoNextCar();
            }
        }

        int numberOfCars = 0;

        while (true) {
            train.gotoPreviousCar();

            numberOfCars++;

            if (train.getLigtsStatusInCar()) {
                break;
            }

            if (numberOfCars == guess && !train.getLigtsStatusInCar()) {
                minimalNumberOfCars = numberOfCars + 1;
                countNumberOfCars();
            }
        }

        System.out.println("Number of cars: " + numberOfCars);
    }

    private int guessNumberOfCars() {
        int guess = minimalNumberOfCars + (int) (Math.random() * 10000);
        return guess;
    }
}