/* -*- coding: utf-8 -*-
 *
 * 1767.cc:  No.1767 BLUE to RED - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 200000;
const int INF = (1U << 31) - 1;
const int MINF = -(1 << 30);

/* typedef */

/* global variables */

int as[MAX_N + 2], bs[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);

  for (int i = 1; i <= n; i++) scanf("%d", as + i);
  as[0] = MINF, as[n + 1] = INF;
  n += 2;

  for (int i = 0; i < m; i++) scanf("%d", bs + i);

  int sum = 0;
  for (int i = 0, k = 0; i < m;) {
    while (as[k + 1] < bs[i]) k++;

    int j = i + 1;
    while (j < m && bs[j] < as[k + 1]) j++;

    int mind = INF;
    for (int l = i; l <= j; l++) {
      int d = 0;
      if (l > i) d += bs[l - 1] - as[k];
      if (l < j) d += as[k + 1] - bs[l];
      mind = min(mind, d);
    }

    sum += mind;

    i = j;
  }

  printf("%d\n", sum);
  return 0;
}