package yukicoder;

import java.util.Scanner;

public class N415 {

	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		int D=sc.nextInt();
		int[] fl=new int[N];
		int pyon=0;
		int now=0;
		fl[0]=1;
		for(int i=1;i<N;i++)
		{
			fl[i]=0;
		}

		while(fl[(now+D>N-1)?now+D-N:now+D]==0)
		{
			pyon++;
			fl[(now+D>N-1)?now+D-N:now+D]=1;
			now=(now+D>N-1)?now+D-N:now+D;
		}
		System.out.println(pyon);
	}

}