#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n)for (int i = 0; i < int(n); ++i)
#define rrep(i,n)for (int i = int(n)-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class T> void chmax(T& a, const T& b) { a = max(a, b); }
template<class T> void chmin(T& a, const T& b) { a = min(a, b); }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  VL a(n), b(m);
  rep(i, n) cin >> a[i];
  constexpr int INF = 1001001001;
  a.push_back(-INF);
  a.push_back(2 * INF);
  n += 2;
  rep(i, m) cin >> b[i];
  sort(all(a));
  sort(all(b));
  int nxt = 0;
  ll ans = 0;
  rep(i, n - 1) {
    int l = nxt, r = nxt;
    while(r < m && b[r] < a[i + 1]) r++;
    if (l == r) continue;
    ans += a[i + 1] - a[i];
    ll mx = max(b[l] - a[i], a[i + 1] - b[r - 1]);
    for(int i = l; i + 1 < r; i++) chmax(mx, b[i + 1] - b[i]);
    ans -= mx;
    nxt = r;
  }
  cout << ans << '\n';
}