#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    // X+Y=X-Y -> Y=0

    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 if(X + Y == 0) {
        cout << 3 << endl;
    } else {
        cout << -1 << endl;
    }
}