G

#include <iostream>
#include <set>
#include <vector>
#include <algorithm>

using namespace std;

#define li long long

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


int gcdex(li a, li b, li& x, li& y) {
	if (a == 0) {
		x = 0; y = 1;
		return b;
	}
	li x1, y1;
	li d = gcdex(b % a, a, x1, y1);
	x = y1 - (b / a) * x1;
	y = x1;
	return d;
}

int main() {
	long long n, q;
	cin >> n >> q;

	if (gcd(n, q) != 1)
		cout << -1;
	else {
		li x, y;
		gcdex(q, n, x, y);
		x = (x % n + n) % n;
		cout << x;
	}
	return 0;
}