using System;

using System.Buffers;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Console.WriteLine(GetLastMethodName("COLIS.APServer.ApplicationLogic.mcon512s.clsCo512Extensions.gSSetTorikomiErrData".AsMemory(), 3).ToString());

    }

            static ReadOnlySpan<char> GetLastMethodName(in ReadOnlyMemory<char> arg, in int number)

        {

            if (number < 0) throw new ArgumentOutOfRangeException(nameof(number));

            var sequence = new ReadOnlySequence<char>(arg);

            //var position = sequence.PositionOf('.');

            var reader = new SequenceReader<char>(sequence);

                reader.Advance(30);

            reader.AdvanceToEnd();

                Console.WriteLine(reader.CurrentSpanIndex);

                Console.WriteLine(reader.Consumed);

                Console.WriteLine(reader.Remaining);

                Console.WriteLine(reader.Sequence.FirstSpan.ToString());

            reader.Advance(reader.Length);

            Console.WriteLine(reader.CurrentSpanIndex);

            for (int index = 0; index < number; index++)

            {

                var lastIndex = reader.CurrentSpan.LastIndexOf('.');

                Console.WriteLine(lastIndex);

                if (lastIndex > 0)

                {

                    reader.Rewind(reader.CurrentSpan.Length - lastIndex);

                    reader.AdvanceToEnd();

                } else

                {

                    break;

                }

            }

            return reader.CurrentSpan;

        }

}