#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
using namespace std;


int main()
{
    int a, b;
    cin >> a >> b;
    if (b == 0) cout << 1 << endl;
    else if (a == -1) cout << 2 << endl;
    else cout << -1 << endl;
}