Problem 3. Inventory

            List<string> items = Console.ReadLine()
                // You will receive a journal with some Collecting items, separated with ', ' (comma and space)
                //.Split(',', StringSplitOptions.RemoveEmptyEntries)
                .Split(", ", StringSplitOptions.RemoveEmptyEntries)
                .ToList();

                else if (command == "Combine Items")
                {
                    string[] itemsToCombine = item.Split(":");

                    string oldItem = itemsToCombine[0];

                    string newItem = itemsToCombine[1];

                    if (items.Contains(oldItem))
                    {
                        // "Combine Items - {oldItem}:{newItem}" – You should check if the old item exists,
                        // if so, add the new item after the old one. Otherwise, ignore the command.
                        //items.Insert((items.IndexOf(item) + 1), newItem);
                        items.Insert((items.IndexOf(oldItem) + 1), newItem);
                    }
                    continue;
                }