#include<bits/stdc++.h>
using namespace std;

#define int long long
#define ll long long
#define pb push_back
#define mp make_pair
#define f(i,a,n) for(int i=a ; i<(int)n ; i++)
#define rf(i,n,a) for(int i=n ; i>=a ; i--)
#define F first
#define S second
#define all(c) (c).begin(),(c).end()
#define sz(v) (int)(v).size()
#define fast ios:: sync_with_stdio(false),cin.tie(nullptr);

typedef long double ld;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef pair<pii,int> ppi;
typedef vector<pii> vpi;

const int inf = 1e9;
const int inf64 = 1e18;
const int MOD = inf + 7;

int32_t main(){
   fast;
   int a,b;
   cin >> a >> b;

   if(b !=0 && a > 0) {
      cout << "-1\n";
      return 0;
   }

   if(b == 0) {
      cout << 1 << "\n";
      return 0;
   }

   if(a == -1) {
      cout << 2 << "\n";
      return 0;
   }

   cout << "-1\n";
}