using System;

using System.Linq;

public class Program

{

    public static bool a(string providerId)

    {

        if (providerId.Length != 8)

        {

            return false;

        }

        if (!int.TryParse(new string(providerId.Take(6).ToArray()), out _))

        {

            return false;

        }               

        var multipliers = new[] {3, 5, 8, 4, 2, 1, 6};

        var cx =0;

        var plv = "0123456789ABCDEFGHJKLMNPQRTUVWXY".ToDictionary(key => key, value => cx++);

        cx = 0;

        var checker = "YXWTLKJHFBA".ToDictionary(key => cx++, value => value);

        var digits = providerId.Take(6).Select(x=>int.Parse($"{x}")).ToArray();

        cx = 0;

        var sum = digits.Take(5).Select(x => x * multipliers[cx++]).Sum() 

            + digits[5]* multipliers[cx++] 

            + plv[providerId[6]] * multipliers[cx];

        return checker[sum % checker.Count] == providerId[7];       

    }

    public static void Main()

    {

        var b="2147371W";

        Console.WriteLine(b+" is "+a(b)+" provider");

    }

}