using System;
using System.Collections.Generic;
using System.Linq;

namespace yukicoder
{
	public class Program
	{
		public static void Main()
		{
			var a = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
			var k = Euclid(a[0] , a[1]);
            if ((a[0] / k + a[1] / k) % 2 == 0)
            {
				k *= 2;
            }
			Console.WriteLine(k);
		}
		static long Euclid(long a, long b)
		{
			var c = Math.Max(a, b);
			var d = Math.Min(a, b);
			var e = c % d;
			if (e > 0)
			{
				return Euclid(e, d);
			}
			else
			{
				return d;
			}
		}
	}
}