use std::io::Read;

fn solve(n: u32, k: u32) {
    if n >= k {
        println!("{}", 2u64.pow(n - k));
    } else {
        println!("{}", 0);
    }
}

fn main() {
    let mut nk = String::new();
    std::io::stdin().read_to_string(&mut nk).ok();
    let nk: Vec<u32> = nk.trim().split('\n').next().unwrap().trim().split_whitespace().map(|s| s.parse::<u32>().unwrap()).collect();
    solve(nk[0], nk[1]);
}