#ifndef LOCAL
#include <bits/stdc++.h>

using namespace std;

#define debug(...) (void(0))
#else
#include "algo/debug.h"
#endif

void solve() {
    int A, B; cin >> A >> B;
    if(B == 0) {
        cout << 1 << endl;
    }else {
        if(A == -1) {
            cout << 2 << endl;
        }else {
            cout << -1 << endl;
        }
    }
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int tt = 1;
    // std::cin >> tt;
    while (tt--) {
        solve();
    }
}