/* 
 *     Author:  srtry
 *     Created: 2025-05-31T11:31:35+09:00
 *     Coding:  utf-8-unix
 */

use proconio::input;
use std::io::{stdout,Write,BufWriter};

fn main() {
    input!{
        a:isize, b:isize
    }

    let out = stdout();
    let mut out = BufWriter::new(out.lock());
    
    if b==0 {
        write!(out, "{}", 1).unwrap();
        return
    }
    if a==-1 {
        write!(out, "{}", 2).unwrap();
        return
    }
    write!(out, "-1").unwrap();
    return
}