#include<stdio.h>
#include<stdlib.h>

int main(void){
	int i,n,d,now=0,cnt=0;
	scanf("%d %d",&n,&d);

	
	int* flag;
	flag = (int*)malloc(sizeof(int)*n);
	for(i=1;i<n;i++) flag[i] = 0;
	flag[0] = 1;

	while(1){
		if(n-1-now >= d) now += d;
		else now = d-n+now;

		if(flag[now] == 0) flag[now] = 1;
		else break;

		cnt++;
	}

	printf("%d\n",cnt);

	return 0;

}