#include <iostream>
#include <vector>
using namespace std;
typedef long long LL;
int main(int argc, char* argv[])
{
	LL N,D;
	cin>>N>>D;
	vector<bool> flag(N+1,false);
	LL aw=0;
	LL i=1;
	flag[1]=true;
	while (i<N){
		i+=D;
		if (i>=N){
			i=i-N;
		}
		if (!flag[i]){
			flag[i]=true;
			aw++;
		}else{
			cout<<aw<<endl;
			return 0;
		}
	}
	return 0;
}