#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr long long MOD = 1000000007;
int main(){
    ll a, b;
    cin >> a >> b;
    ll cnt = 0;
    ll tmp = 0;
    if (b == 0) cout << "1" << endl;
    else if (a==-1)
        cout << "2" << endl;
    else
        cout << "-1" << endl;
}