#![allow(unused_imports)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;
use std::ops::Bound::*;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

fn main() {
    let v = read_vec::<usize>();
    let (n, m) = (v[0], v[1]);
    let a = read_vec::<i64>();
    let b = read_vec::<i64>();

    let mut events = vec![];
    for &anum in &a {
        events.push((anum, 'A'));
    }
    for &bnum in &b {
        events.push((bnum, 'B'));
    }
    events.sort();

    let mut ans = 0;
    let mut q = BinaryHeap::new();
    let mut ab_found = false;
    for i in 0..events.len() - 1 {
        let prev = events[i];
        let cur = events[i + 1];

        if prev.1 == 'A' && cur.1 == 'A' {
            continue;
        }
        q.push(Reverse(cur.0 - prev.0));
        if prev.1 == 'A' && cur.1 == 'B' {
            ab_found = true;
        }
        if prev.1 == 'B' && cur.1 == 'A' {
            if ab_found {
                while q.len() > 1 {
                    ans += q.pop().unwrap().0;
                }
            } else {
                while q.len() > 0 {
                    ans += q.pop().unwrap().0;
                }
            }
            q.clear()
        }
    }
    while q.len() > 0 {
        ans += q.pop().unwrap().0;
    }
    println!("{}", ans);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}