#include <bits/stdc++.h>

#define M_PI       3.14159265358979323846   // pi

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> VI;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> t3;
typedef tuple<ll, ll, ll, ll> t4;

#define rep(a,n) for(ll a = 0;a < n;a++)
#define repi(a,b,n) for(ll a = b;a < n;a++)

#include <bits/stdc++.h>
using namespace std;

const ll mod = 1e9 + 7;

const ll INF = 1e15;


ll solve(ll a, ll b, ll k) {
	if (k == 0) {
		return b;
	}
	return a * solve(a, b, k - 1) + b;
}

int main() {
	ll a, b;
	cin >> a >> b;

	if (b == 0) cout << 1 << endl;
	else if (a == -1) {
		cout << 2 << endl;
	}
	else {
		cout << -1 << endl;
	}
	//for (int c = -100; c < 100; c++) {
	//	for (int d = -100; d < 100; d++) {
	//		for (int i = 0; i < 10; i++) {
	//			auto s = solve(c, d, i);
	//			if (s == 0) {
	//				cout << c << " " << d << " " << i << endl;
	//			}
	//		}
	//	}
	//}

	//for (int i = 0; i < 5; i++) {
	//	cout << solve(a, b, i) << endl;;
	//}
	return 0;
}