using System;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
public class Test
{
public static void Main()
{
var s = "Hi this is Bob.";
var results = Regex.Matches(s, @"(?=\b(\w+(?:[\s,]+\w+){2})\b)")
.Cast<Match>()
.Select(p => p.Groups[1].Value)
.ToList();
Console.WriteLine(String.Join(", ", results));
}
}
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