#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;
constexpr int INF = 2e9;

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