#include <iostream>
using namespace std;
int main(){
    int a,b;cin>>a>>b;
    if(a==b){
        cout << 0 << endl;
    }else if(b == 0){
        cout << 1 << endl;
    }else if(a == 0){
        cout << 2 << endl;
    }else{
        cout << -1 << endl;
    }
}