use std::collections::{BTreeSet, HashMap};

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: Vec<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: Vec<usize> = b.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut pos = a.iter().copied().collect::<BTreeSet<usize>>();
    for &v in b.iter() { pos.insert(v); }
    let mapping = pos.iter().enumerate().map(|(i, &v)| (v, i)).collect::<HashMap<_, _>>();
    let revmap = pos.iter().copied().collect::<Vec<_>>();
    let a = a.into_iter().map(|v| *mapping.get(&v).unwrap()).collect::<Vec<_>>();
    let b = b.into_iter().map(|v| *mapping.get(&v).unwrap()).collect::<Vec<_>>();
    let mut uf = UnionFind::new(pos.len());
    for i in 0..n-1 { uf.unite(a[i], a[i+1]); }
    let mut lines = (0..pos.len()-1).map(|i| (i, revmap[i+1]-revmap[i])).collect::<Vec<_>>();
    lines.sort_by_key(|&(_, v)| v);
    let mut result = 0usize;
    for &(i, cost) in lines.iter() {
        if uf.find(i) == uf.find(i+1) { continue; }
        uf.unite(i, i+1);
        result += cost;
    }
    println!("{}", result);
}