#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

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;
  return 0;
}