fn main() {
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).ok();
	let v: Vec<i64> = s.split_whitespace().flat_map(str::parse).collect();
	println!(
		"{}",
		match v.as_slice() {
			[_, 0] => 1,
			[-1, _] => 2,
			_ => -1,
		}
	)
}