#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;

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