use proconio::input;
use std::mem::swap;
use std::cmp::min;

fn main(){
    input!{
        mut a: i32,
        mut b: i32,
    }

    if a < b{
        swap(&mut a, &mut b);
    }
    let mut c = 1;
    while c*2 <= a{
        c *= 2;
    }

    println!("{}", min(c-1, b))
}