using System;
using System.IO;
using System.Text.RegularExpressions;
 
public class Test
{
	public static void Main()
	{
		var lines = new string[] {"abc1234abc", "abc12345abc", "abc123/456abc", "abc1234/1234abc"};
        foreach (string s in lines) 
        {
            var matches = Regex.Matches(s, @"(?<![\d/])(?<num>\d{1,4})(?![\d/])|/(?<num>\d{1,3})(?!\d)");
            foreach (Match m in matches)
        		Console.WriteLine(m.Groups["num"].Value);
        }
	}
}

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