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

#ifdef DEBUG_
#include <compe/debug.hpp>
#else
#define dump(...)
#endif

#define FastIO cin.tie(nullptr), ios_base::sync_with_stdio(false);
#define rep(i, n) for (int i = 0; (int)i < n; ++i)
#define output(msg) cout << (msg) << '\n'
#define die(msg)         \
  do {                   \
    cout << msg << endl; \
    exit(0);             \
  } while (0)
#define INTi 1 << 30
#define INFll 1LL << 60

template <typename T> bool chmax(T& a, const T& b) {
  return ((a < b) ? (a = b, true) : (false));
}
template <typename T> bool chmin(T& a, const T& b) {
  return ((a > b) ? (a = b, true) : false);
}

using llint = long long int;

int main() {
  FastIO;
  llint a, b;
  cin >> a >> b;

  /*
   * 1. an + b
   *
   * 2. aan + ab + b
   *
   * 3. aa(an + b) + ab + b
   *    aaan + aab + ab + b
   * */
  if (b == 0) die(1);
  if (a >= 0 && b >= 0) die(-1);
  if (a == -1) die(2);
  output(-1);

  // aan + ab + b
  // -b -b

  // -2, -2
  // an + b = -2
  // -2*-2 -2 = 2
  // 2 * -2 -2 = -6
  // 12 -2 = 10
  // -20 -2 -22 ...
}