using System;

using System.Text.RegularExpressions;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var thing = new Thing();

        Console.WriteLine(thing.SplitSpace());

        Console.WriteLine(thing.Regexp());

        Console.WriteLine(thing.Substring());

        Console.WriteLine(thing.Span());

​

    }

}

​

public class Thing

{

    string s = "Step Y must be finished before step A can begin.";

​

    public (string a, string b) SplitSpace()

    {

        var split = s.Split(" ");

        var a = split[1];

        var b = split[7];

        return(a,b);

    }

​

    public (string a, string b) Regexp()

    {

        var match = Regex.Matches(s, "Step (?'a'.) must be finished before step (?'b'.) can begin.").First().Groups;

        var a = match["a"].Value;

        var b = match["b"].Value;

        return(a,b);

    }

​

    public (string a, string b) Substring()

    {

        var a = s.Substring(s.IndexOf(' ') + 1, 1);

        var b = s.Substring(s.LastIndexOf(" can begin.") - 1, 1);

        return(a,b);

    }

​

    public (string a, string b) Span()

    {

        var span = s.AsSpan();

        var a = span.Slice(span.IndexOf(' ') + 1, 1);

        var b = span.Slice(span.LastIndexOf(" can begin.") - 1, 1);

        return (new string(a), new string(b));

    }

}