#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
    long long A, B;
    cin >> A >> B;
    if(A == 0 && B != 0){
        cout << -1 << endl;
        return 0;
    }
    else if(B == 0){
        cout << 1 << endl;
        return 0;
    }
    else{
        if(A == -1){
            cout << 2 << endl;
            return 0;
        }
        cout << -1 << endl;
    }
}