using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace yuki415
{
    class Program
    {
        static void Main(string[] args)
        {
            var a = scan;
            int n = a[0];
            int d = a[1];
            if (n % d == 0)
            {
                Console.WriteLine(n / d - 1);
            }
            else
            {
                var t = new bool[n];
                t[0] = true;
                int cnt=0;
                int i = 0;
                while (true)
                {
                    if (i + d > n - 1) i -= n;
                    if (t[i + d] == true) break;
                    else
                    {
                        cnt++;
                        t[i + d] = true;
                        i += d;
                    }
                }
                Console.WriteLine(cnt);
            }
        }

        static int[] scan
        {
            get { return Console.ReadLine().Split().Select(int.Parse).ToArray(); }
        }
    }
}