Snowflake

using System;
using System.Text.RegularExpressions;

namespace Problem03Exam05012018
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            const string surfacePattern = @"[^a-zA-Z0-9]+";
            const string mantlePattern = @"[0-9_]+";
            const string corePattern = @"([a-zA-Z]+)";

            var core = string.Empty;

            var input = Console.ReadLine();
            var matcher = Regex.Match(input, $@"^{surfacePattern}$");

            if (!matcher.Success)
            {
                Console.WriteLine("Invalid");
                return;
            }

            input = Console.ReadLine();
            matcher = Regex.Match(input, $@"^{mantlePattern}$");

            if (!matcher.Success)
            {
                Console.WriteLine("Invalid");
                return;
            }

            input = Console.ReadLine();
            var linePattern = $@"^{surfacePattern}{mantlePattern}{corePattern}{mantlePattern}{surfacePattern}$";
            matcher = Regex.Match(input, linePattern);

            if (matcher.Success)
            {
                core = matcher.Groups[1].Value;
            }
            else
            {
                Console.WriteLine("Invalid");
                return;
            }

            input = Console.ReadLine();
            matcher = Regex.Match(input, $@"^{mantlePattern}$");

            if (!matcher.Success)
            {
                Console.WriteLine("Invalid");
                return;
            }

            input = Console.ReadLine();
            matcher = Regex.Match(input, $@"^{surfacePattern}$");

            if (!matcher.Success)
            {
                Console.WriteLine("Invalid");
                return;
            }

            Console.WriteLine("Valid");
            Console.WriteLine(core.Length);
        }
    }
}