use std::{collections::{BTreeSet, HashMap, BinaryHeap}, cmp::Reverse};

struct UnionFind {
    n: usize,
    parents: Vec<usize>,
    depths: Vec<usize>,
    chains: Vec<usize>,
}

impl UnionFind {
    fn new(n: usize) -> Self {
        UnionFind {
            n: n,
            parents: (0..n).collect(),
            depths: vec![0; n],
            chains: vec![1; n],
        }
    }

    fn equiv(&mut self, a: usize, b: usize) -> bool {
        self.find(a) == self.find(b)
    }
    
    fn unite(&mut self, a: usize, b: usize) {
        if self.equiv(a, b) { return; }
        let x = self.parents[a];
        let y = self.parents[b];
        if self.depths[x] > self.depths[y] {
            self.parents[x] = self.parents[y];
            self.chains[y] += self.chains[x];
        } else {
            self.parents[y] = self.parents[x];
            self.chains[x] += self.chains[y];
            if self.depths[x] == self.depths[y] {
                self.depths[x] += 1;
            }
        }
    }

    fn find(&mut self, a: usize) -> usize {
        if self.parents[a] == a { return a; }
        let p = self.find(self.parents[a]);
        self.parents[a] = p;
        p
    }

    fn chain_cnt(&mut self, i: usize) -> usize {
        let idx = self.find(i);
        self.chains[idx]
    }
}

fn main() {
    let mut nm = String::new();
    std::io::stdin().read_line(&mut nm).ok();
    let nm: Vec<usize> = nm.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nm[0];
    let m = nm[1];
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: BTreeSet<usize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let mut b = String::new();
    std::io::stdin().read_line(&mut b).ok();
    let b: BTreeSet<usize> = b.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut uf = UnionFind::new(n+m+1);
    let mut totals = BTreeSet::new();
    for &v in a.iter() { totals.insert(v); }
    for &v in b.iter() { totals.insert(v); }
    let mapping = (0..n+m).map(|i| (*totals.iter().nth(i).unwrap(), i)).collect::<HashMap<usize, usize>>();
    for &v in a.iter() {
        uf.unite(*mapping.get(&v).unwrap(), n+m);
    }
    let mut pque = BinaryHeap::new();
    for &v in b.iter() {
        let idx = *mapping.get(&v).unwrap();
        if let Some(&left) = a.range(..v).rev().nth(0) {
            let nidx = *mapping.get(&left).unwrap();
            pque.push((Reverse(v-left), idx, nidx));
        }
        if let Some(&right) = a.range(v+1..).nth(0) {
            let nidx = *mapping.get(&right).unwrap();
            pque.push((Reverse(right-v), idx, nidx));
        }
        if let Some(&left) = b.range(..v).rev().nth(0) {
            let nidx = *mapping.get(&left).unwrap();
            pque.push((Reverse(v-left), idx, nidx));
        }
        if let Some(&right) = b.range(v+1..).nth(0) {
            let nidx = *mapping.get(&right).unwrap();
            pque.push((Reverse(right-v), idx, nidx));
        }
    }
    let mut result = 0usize;
    while let Some((Reverse(cost), l, r)) = pque.pop() {
        if uf.find(l) == uf.find(r) { continue; }
        uf.unite(l, r);
        result += cost;
    }
    println!("{}", result);
}