using System;

public class Program

{

    public static void Main()

    {

        var wagerUid = 1000960221234860032;

        var lengthLimit = 20;

        var prefix = "64";

        var power = lengthLimit - prefix.Length;

        var wagerNo = $"{prefix}{(decimal)(wagerUid % (Math.Pow(10, power) - 1))}";

        Console.WriteLine(wagerNo);

        Console.WriteLine(wagerNo.Length);

    }

}