#include <algorithm>
#include <cstring>
#include <deque>
#include <iostream>
#include <limits>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#define rep(i, a, n) for(int i = a; i < n; i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

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