Diamond Problem

            string input = Console.ReadLine();

            bool isDiam = false;

            int startIndex = input.IndexOf("<");
            while (startIndex != - 1)
            {
                int endIndex;
                string diamond = string.Empty;

                endIndex = input.IndexOf(">", startIndex + 1);

                if (endIndex - startIndex > 0)
                {
                    diamond = input.Substring(startIndex + 1, endIndex - startIndex - 1);
                }

                startIndex = input.IndexOf("<", startIndex + 1);

                int sum = 0;
                for (int i = 0; i < diamond.Length; i++)
                {
                    if (Char.IsDigit(diamond[i]))
                    {
                        sum += diamond[i] - '0';
                    }
                }
                if (sum > 0)
                {
                    Console.WriteLine($"Found {sum} carat diamond");
                    isDiam = true;
                }
            }

            if (!isDiam)
            {
                Console.WriteLine("Better luck next time");
            }