fn main() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let mut itr = s.trim().split_ascii_whitespace();
    let mut a: usize = itr.next().unwrap().parse().unwrap();
    let mut b: usize = itr.next().unwrap().parse().unwrap();
    
    if a < b { std::mem::swap(&mut a , &mut b); }

    let mut bit = 1;
    while bit * 2 <= a { bit *= 2; }

    println!("{}", std::cmp::min(bit - 1, b));    
}