#include <bits/stdc++.h>

using namespace std;

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = long long;
using P = std::tuple<int,int>;

const int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1}, dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    int X, Y;
    std::cin >> X >> Y;

    int res = -1;
    if(X == Y){
        res = 0;
    }else if(Y == 0){
        res = 1;
    }else if(X == 0){
        res = 2;
    }
    std::cout << res << std::endl;
}