/*
************************
Höfundur: Ragnar Geir Brynjólfsson
Dags:     06/2010
Forrit sem ber kennsl á 
kennimerki í C#
***********************
*/
using System;
using System.Text.RegularExpressions;
class T203Sd7_1 {
  static void Main() {
     Console.Write("Sláðu inn kennimerki: ");
     String numer = Console.ReadLine();
     String mynstur=@"^[a-z,A-Z,_][a-z,A-Z,0-9_]{1,512}\z";
     if (Regex.IsMatch(numer, mynstur)) {
        Console.WriteLine("Leyfilegt kennimerki.");
     } else {
        Console.WriteLine("Óleyfilegt kennimerki.");
     }
  }
}