Задача по дизайну: Система для бронирования мест

SeatReserver.cs

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.
	}
}