#include <iostream>
#include <sstream>

using namespace std;

int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }

int main(int argc, char *argv[])
{
	int N, D;
	cin >> N >> D;
	int ans = 0;
	D %= N;
	if (D > 0) {
		int c = N / D;
		int d = c * D;
		if (gcd(N, d) > 1) {
			N = c;
		}
		ans = N - 1;
	}
	cout << ans << endl;
	return 0;
}