using System;

public class Program

{

    public static void Main()

    {

        int? sid = null;

        int? scode = 20201;

        Console.WriteLine(validate(sid, scode));

        sid = 44; scode = null;

        Console.WriteLine(validate(sid, scode));

        sid = null; scode = 11111;

        Console.WriteLine(validate(sid, scode));

        sid = 58; scode = 19982;

        Console.WriteLine(validate(sid, scode));

        sid = null; scode = null;

        Console.WriteLine(validate(sid, scode));

    }

    public static int sessionCacheConvertSessionCode(int sessioncode)

    {

        int d = 0;

        if(sessioncode != 11111)

        {

            d = 12;

        }

        return d;

    }

    public static string validate(int? sessionID, int? sessionCode)

    {

        string convertedSessionID = "0";

        if (sessionID.HasValue && sessionID.Value > 0) { convertedSessionID = sessionID.Value.ToString(); }

        if (convertedSessionID == "0" && sessionCode.HasValue && sessionCode.Value > 0) { convertedSessionID = "determined ..." + sessionCacheConvertSessionCode(sessionCode.Value).ToString(); }

        if (convertedSessionID == "0" || convertedSessionID == "determined ...0") { return "Must provide either a valid Session ID or Session Code"; }

        return convertedSessionID;

    }

}