#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
#define rep(i, a, b) for(ll i = a; i < b; ++i)
#define rrep(i, a, b) for(ll i = a; i >= b; --i)
constexpr ll inf = 4e18;
struct SetupIO {
    SetupIO() {
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout << fixed << setprecision(30);
    }
} setup_io;
template <typename T = int>
struct Edge {
    int from, to;
    T cost;
    int idx;
    Edge()
        : from(-1), to(-1), cost(-1), idx(-1) {}
    Edge(int from, int to, T cost = 1, int idx = -1)
        : from(from), to(to), cost(cost), idx(idx) {}
    operator int() const {
        return to;
    }
};
template <typename T = int>
struct Graph {
    Graph(int N)
        : n(N), es(0), g(N) {}
    int size() const {
        return n;
    }
    int edge_size() const {
        return es;
    }
    void add_edge(int from, int to, T cost = 1) {
        assert(0 <= from and from < n);
        assert(0 <= to and to < n);
        g[from].emplace_back(from, to, cost, es);
        g[to].emplace_back(to, from, cost, es++);
    }
    void add_directed_edge(int from, int to, T cost = 1) {
        assert(0 <= from and from < n);
        assert(0 <= to and to < n);
        g[from].emplace_back(from, to, cost, es++);
    }
    inline vector<Edge<T>>& operator[](const int& k) {
        assert(0 <= k and k < n);
        return g[k];
    }
    inline const vector<Edge<T>>& operator[](const int& k) const {
        assert(0 <= k and k < n);
        return g[k];
    }

   private:
    int n, es;
    vector<vector<Edge<T>>> g;
};
template <typename T = int>
using Edges = vector<Edge<T>>;
struct UnionFind {
    UnionFind(int N)
        : n(N), data(N, -1) {}
    int merge(int a, int b) {
        assert(0 <= a and a < n);
        assert(0 <= b and b < n);
        int x = leader(a), y = leader(b);
        if(x == y) return x;
        if(-data[x] < -data[y]) swap(x, y);
        data[x] += data[y];
        data[y] = x;
        return x;
    }
    bool same(int a, int b) {
        assert(0 <= a and a < n);
        assert(0 <= b and b < n);
        return leader(a) == leader(b);
    }
    int leader(int a) {
        assert(0 <= a and a < n);
        if(data[a] < 0) return a;
        return data[a] = leader(data[a]);
    }
    int size(int a) {
        assert(0 <= a and a < n);
        return -data[leader(a)];
    }
    vector<vector<int>> groups() {
        vector<int> leader_buf(n), group_size(n);
        for(int i = 0; i < n; ++i) {
            leader_buf[i] = leader(i);
            ++group_size[leader_buf[i]];
        }
        vector<vector<int>> result(n);
        for(int i = 0; i < n; ++i) {
            result[i].reserve(group_size[i]);
        }
        for(int i = 0; i < n; ++i) {
            result[leader_buf[i]].push_back(i);
        }
        result.erase(remove_if(result.begin(), result.end(), [&](const vector<int>& v) { return v.empty(); }), result.end());
        return result;
    }

   private:
    int n;
    vector<int> data;
};
template <typename T>
pair<T, Edges<T>> kruskal(int n, Edges<T> es) {
    sort(es.begin(), es.end(), [&](const Edge<T>& a, const Edge<T>& b) { return a.cost < b.cost; });
    UnionFind uf(n);
    T cost = 0;
    Edges<T> res;
    res.reserve(n - 1);
    for(const auto& e : es) {
        if(uf.same(e.from, e.to)) continue;
        cost += e.cost;
        uf.merge(e.from, e.to);
        res.emplace_back(e);
    }
    return {cost, res};
}
int main(void) {
    int n, m;
    cin >> n >> m;
    vector<int> a(n), b(m);
    Edges<ll> e;
    rep(i, 0, n) {
        cin >> a[i];
        e.push_back({(int)i, n + m, 0});
    }
    rep(i, 0, m) {
        cin >> b[i];
        if(i > 0) e.push_back({n + (int)i, n + (int)i - 1, b[i] - b[i - 1]});
        int idx = lower_bound(a.begin(), a.end(), b[i]) - a.begin();
        if(idx < n) e.push_back({n + (int)i, idx, a[idx] - b[i]});
        if(idx > 0) e.push_back({n + (int)i, idx - 1, b[i] - a[idx - 1]});
    }
    cout << kruskal(n + m + 1, e).first << '\n';
}