using System;
using System.Text.RegularExpressions;
public class MainClass {
public static void Main() {
Regex n = new Regex("Gr(a|e)y");
MatchCollection mp = n.Matches("Green, Grey, Granite, Gray");
for (int i = 0; i < mp.Count; i++) {
Console.WriteLine("Found '{0}' at position {1}",mp[i].Value, mp[i].Index);
}
}
}