Extract sentences by keyword

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace _2.Extract_sentences_by_keyword
{
    class Program
    {
        static void Main(string[] args)
        {
            string word = Console.ReadLine();
            string text = Console.ReadLine();

            string pattern = @"(?:^|[\s|\w]+) word [a-zA-Z0-9]+[\sa-z-0-9]+";

            var replaced = pattern.Replace("word", word);
            var reg = new Regex(replaced);

            MatchCollection matchCollection = reg.Matches(text);

            foreach (Match match in matchCollection)
            {
                Console.WriteLine(match.Groups[0]);
            }


        }
    }
}