fn main() {
    let mut ab = String::new();
    std::io::stdin().read_line(&mut ab).ok();
    let ab: Vec<usize> = ab.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let a = ab[0];
    let b = ab[1];
    let abits = format!("{:b}", a);
    let bbits = format!("{:b}", b);
    if abits.len() != bbits.len() {
        println!("{}", a.min(b));
    } else {
        println!("{}", (1usize << abits.len()) - 1 - (1usize << (abits.len() - 1)));
    }
}