#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

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

    if (b == 0) {
        cout << 1 << endl;
        exit(0);
    }

    if (a == 0) {
        cout << -1 << endl;
        exit(0);
    }

    if (a == -1) {
        cout << 2 << endl;
        exit(0);
    }

    cout << -1 << endl;

    return 0;
}