public class Main {
    public static void main(String[] args) {
        Train train = new Train(5000, 5000);
 
        Counter counter = new Counter(train);
 
        counter.countNumberOfCars();
    }
}
 
class Car {
    private boolean isLightOn;
 
    Car() {
        switch((int) (Math.random() * 2)) {
            case 0:
                setLightOn(false);
 
                break;
            case 1:
                setLightOn(true);
 
                break;
        }
    }
 
    void setLightOn(boolean isLightOn) {
        this.isLightOn = isLightOn;
    }
 
    boolean isLightOn() {
        return isLightOn;
    }
}
 
public class Train {
    private Car[] cars;
 
    private int size;
 
    Train(int minimalSize, int maximumSize) {
        size = minimalSize + (int) (Math.random() * (maximumSize - minimalSize + 1));
 
        cars = new Car[size];
 
        for(int i = 0; i < size; i++)
            cars[i] = new Car();
    }
 
    Car getCar() {
        return cars[0];
    }
 
    void goToNextCar() {
        Car temp = cars[0];
 
        for(int i = 0; i < size - 1; i++)
            cars[i] = cars[i + 1];
 
        cars[size - 1] = temp;
    }
 
    void goToPreviousCar() {
        Car temp = cars[size - 1];
 
        for(int i = size - 1; i > 0; i--)
            cars[i] = cars[i - 1];
 
        cars[0] = temp;
    }
}
 
public class Counter {
    private Train train;
 
    Counter(Train train) {
        this.train = train;
    }
 
    private int minimalNumberOfCars;
 
    void countNumberOfCars() {
        int guess = guessNumberOfCars();
 
        System.out.println("Number of cars where should stop: " + guess);
 
        int i = 0;
 
        while(true) {
            Car car = train.getCar();
 
            i++;
 
            if(i == guess) {
                car.setLightOn(true);
 
                break;
            } else {
                car.setLightOn(false);
 
                train.goToNextCar();
            }
        }
 
        int numberOfCars = 0;
 
        while(true) {
            train.goToPreviousCar();
 
            Car car = train.getCar();
 
            numberOfCars++;
 
            if(car.isLightOn())
                break;
 
            if(numberOfCars == guess && !car.isLightOn()) {
                minimalNumberOfCars = numberOfCars + 1;
 
                countNumberOfCars();
            }
        }
 
        System.out.println("Number of cars: " + numberOfCars);
    }
 
    private int guessNumberOfCars() {
        int guess = minimalNumberOfCars + (int) (Math.random() * 10000);
 
        return guess;
    }
}