using System;

internal static class Program
{
    private static void Main(string[] args)
    {
        var session = new BookingSession(8);
        Console.WriteLine($"First: {session.Reserve(5)}");
        Console.WriteLine($"Excess: {session.Reserve(4)}");
        Console.WriteLine($"Exact: {session.Reserve(3)}");
        Console.WriteLine($"Reserved: {session.Reserved}");
    }
}

internal sealed class BookingSession
{
    public int Capacity { get; }
    public int Reserved { get; private set; }
    public BookingSession(int capacity)
    {
        if (capacity is < 1 or > 1000) throw new ArgumentOutOfRangeException(nameof(capacity));
        Capacity = capacity;
    }
    public bool Reserve(int requested)
    {
        if (requested < 1 || requested > Capacity - Reserved) return false;
        Reserved += requested; return true;
    }
}