import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author silviase
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        No1047ZeroNovice solver = new No1047ZeroNovice();
        solver.solve(1, in, out);
        out.close();
    }

    static class No1047ZeroNovice {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            long a = in.nextLong();
            long b = in.nextLong();

            if (b == 0) {
                out.println(1);
                return;
            }

            // b != 0{
            if (a == -1) {
                out.println(2);
                return;
            }

            out.println(-1);
        }

    }
}