using System;

using System.Collections.Generic;

public class Program

{

    public class SeatReserver

    {

        private int N;

        private PriorityQueue<int, int> availableSeats;

        public SeatReserver(int n) {

            N = n;

            availableSeats = new PriorityQueue<int, int>();

            for (int i = 1; i <= n; i++)

            {

                availableSeats.Enqueue(i, i);

            }

        }

​

        public int Reserve() {

            if (availableSeats.Count == 0)

            {

                throw new Exception("There are no more available seats.");

            }

            return availableSeats.Dequeue();

        }

​

        public void Unreserve(int num) {

            if (num > N)

            {

                throw new Exception("Num is larger than the max size N.");

            }

            availableSeats.Enqueue(num, num);

        }

    }

    private static void Print(int n)

    {

        Console.WriteLine(n.ToString());

    }

    public static void Main()

    {

        Console.WriteLine("UniLecs");

        // tests

        var seatReserver = new SeatReserver(5);

        Print(seatReserver.Reserve()); // 1

        Print(seatReserver.Reserve()); // 2

        seatReserver.Unreserve(2); // 2е место снова доступно

        Print(seatReserver.Reserve()); // 2

        Print(seatReserver.Reserve()); // 3

        Print(seatReserver.Reserve()); // 4

        Print(seatReserver.Reserve()); // 5

        Print(seatReserver.Reserve()); // Exception: There are no more free seats.

        seatReserver.Unreserve(6); // Exception: Num is larger than the max size N.

    }

}