using System;

public class Program

{

    public static void Main(string[] args)

    {

        double a, b, r;

        a = 30;

        b = 12;

        while(true)

        {r = a % b; a=b; b=r;

          if (b==0) break;

        }

        Console.WriteLine("a = {0}" , a);

    }

}