#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <limits.h>
#include <map>
#include <queue>
#include <set>
#include <string.h>
#include <vector>

using namespace std;
typedef long long ll;

struct Node {
  int a_idx;
  int b_idx;
  int dist;

  Node(int a_idx = -1, int b_idx = -1, int dist = -1) {
    this->a_idx = a_idx;
    this->b_idx = b_idx;
    this->dist = dist;
  }

  bool operator>(const Node &n) const {
    return dist > n.dist;
  }
};

int main() {
  int N, M;
  cin >> N >> M;

  vector<int> A(N);
  for (int i = 0; i < N; ++i) {
    cin >> A[i];
  }

  vector<int> B(M);
  for (int i = 0; i < M; ++i) {
    cin >> B[i];
  }
  priority_queue <Node, vector<Node>, greater<Node>> pque;

  for (int i = 0; i < N; ++i) {
    int a = A[i];
    auto it = lower_bound(B.begin(), B.end(), a);
    int idx;

    if (it == B.end()) {
      idx = B.size() - 1;
    } else {
      idx = it - B.begin();
    }

    // fprintf(stderr, "idx: %d, a: %d, b: %d\n", idx, a, B[idx]);
    pque.push(Node(i, idx, abs(a - B[idx])));
    if (0 <= idx - 1) {
      pque.push(Node(i, idx - 1, abs(a - B[idx - 1])));
    }
    if (idx + 1 < M) {
      pque.push(Node(i, idx + 1, abs(a - B[idx + 1])));
    }
  }

  bool checked[M];
  memset(checked, false, sizeof(checked));
  ll ans = 0;

  while (not pque.empty()) {
    Node node = pque.top();
    pque.pop();

    if (checked[node.b_idx]) continue;
    checked[node.b_idx] = true;
    ans += node.dist;

    // fprintf(stderr, "%d - %d\n", B[node.b_idx], node.dist);

    if (0 <= node.b_idx - 1 && not checked[node.b_idx - 1]) {
      pque.push(Node(node.a_idx, node.b_idx - 1, abs(B[node.b_idx] - B[node.b_idx - 1])));
    }
    if (node.b_idx + 1 < M && not checked[node.b_idx + 1]) {
      pque.push(Node(node.a_idx, node.b_idx + 1, abs(B[node.b_idx] - B[node.b_idx + 1])));
    }
  }

  cout << ans << endl;

  return 0;
}