#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using namespace atcoder;
//using mint = modint998244353;
using mint = modint1000000007;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
using tlll = tuple<ll, ll, ll>;
constexpr ll INF = 1LL << 60;
template<class T> bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
ll safemod(ll A, ll M) {return (A % M + M) % M;}
ll divfloor(ll A, ll B) {if (B < 0) {return divfloor(-A, -B);} return (A - safemod(A, B)) / B;}
ll divceil(ll A, ll B) {if (B < 0) {return divceil(-A, -B);} return divfloor(A + B - 1, B);}
#define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false)

#include <atcoder/dsu>

int main()
{
  ll N, M;
  cin >> N >> M;
  vector<ll> A(N), B(M);
  for (ll i = 0; i < N; i++)
  {
    cin >> A.at(i);
  }
  for (ll i = 0; i < M; i++)
  {
    cin >> B.at(i);
  }

  dsu ds(N + M);
  for (ll i = 0; i < N - 1; i++)
  {
    ds.merge(i, i + 1);
  }

  vector<pll> C(N + M);
  for (ll i = 0; i < N; i++)
  {
    C.at(i) = make_pair(A.at(i), i);
  }
  for (ll i = 0; i < M; i++)
  {
    C.at(N + i) = make_pair(B.at(i), N + i);
  }
  sort(C.begin(), C.end());

  vector<tlll> E;
  for (ll i = 0; i < N + M - 1; i++)
  {
    ll u = C.at(i).second, v = C.at(i + 1).second;
    ll d = C.at(i + 1).first - C.at(i).first;
    if (!ds.same(u, v))
      E.push_back(make_tuple(d, u, v));
  }
  sort(E.begin(), E.end());

  ll ans = 0;
  for (auto e : E)
  {
    auto [d, u, v] = e;
    if (!ds.same(u, v))
    {
      ds.merge(u, v);
      ans += d;
    }
  }
  cout << ans << endl;
}