#include<iostream>

using namespace std;

int main() {

	int x, y;

	cin >> x >> y;

	if (x == y)cout << 0 << endl;
	else if (x != 0 && y == 0)cout << 1 << endl;
	else if (x == 0 && y != 0)cout << 2 << endl;
	else cout << -1 << endl;
	
	return 0;
}