public class Vehicle {
    private String type;
    private String way;
    private int maxSpeed;
    public Vehicle(String type, String way, int maxSpeed) {
        this.type = type;
        this.way = way;
        this.maxSpeed = maxSpeed;
    }
}

public class Train extends Vehicle {
    private int numOfCarriages;
    public Train(int maxSpeed, int numOfCarriages) {
        super("land", "tracks", maxSpeed);
        this.numOfCarriages = numOfCarriages;
    }
    public void incNumOfCarriages(int n) {
        this.numOfCarriages = this.numOfCarriages + n;
    }
}

public class Boat extends Vehicle {
    public Boat(String way, int maxSpeed) {
        super("water", way, maxSpeed);
    }
}

public class Airplane extends Vehicle {
    private int maxHeight;
    public Airplane(int maxSpeed, int maxHeight) {
        super("sky", "air", maxSpeed);
        this.maxHeight = maxHeight;
    }
}

public class TransportationCompany {
    private Vehicle[] vehicles = new Vehicle[50];
    private int counter = 0;
    public void addVehicle(Vehicle v) {
        this.vehicles[counter] = v;
        this.counter++;
    }
}