fn main() {
    let mut input = String::new();
    std::io::stdin().read_line(&mut input).unwrap();
    let mut iter = input.split_whitespace();
    let mut A: i32 = iter.next().unwrap().parse().unwrap();
    let mut B: i32 = iter.next().unwrap().parse().unwrap();
    // swap a b if a >b
    if A > B {
        let temp = A;
        A = B;
        B = temp;
    }
    // find biggest 2^a <= A and 2^b <= B
    let mut a = 1;
    let mut b = 1;
    while a * 2 <= A {
        a *= 2;
    }
    while b * 2 <= B {
        b *= 2;
    }
    if a < b {
        println!("{}", A);
    } else if a == b {
        println!("{}", a - 1);
    }
}