using System; using System.Collections.Generic; using System.Globalization; using System.Text; using System.Text.RegularExpressions; using System.Reflection;
public class MainClass{
public static void Main(){
Regex r = new Regex(@"(^\d+$\n)+", RegexOptions.Multiline);
Console.WriteLine(r.Match("987987\n129821").Value);
}
}