#include<iostream>
#include <math.h>
#include <string>
#include <iomanip>
using namespace std;

int main(){
	int n,d;
	int a=1;
	int cnt = 0;
	cin >> n >> d;
	while (-1){
		a = a + d;
		if (a > n){
			a = a - n;
		}
		if (a == 1){
			break;
		}
		cnt++;
	}
	cout << cnt << endl;



	return 0;
}