#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

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