#include <bits/stdc++.h>
using namespace std;
inline long long msb(long long val) { return 63 - __builtin_clzll(val); }
inline int msb(int val) { return 31 - __builtin_clz(val); }
template <class T>
bool chmin(T& a, const T& b) {
  return a > b ? a = b, true : false;
}
template <class T>
bool chmax(T& a, const T& b) {
  return a < b ? a = b, true : false;
}
const long long mod = 1e9 + 7, N = 2e5 + 5;
long long a[N], n, m, k;
long long b[N];
void solve(long long test_case) {
  long long i, j, ans = 0;
  cin >> n >> m;
  for (i = 0; i < n; i++) cin >> a[i];
  for (i = 0; i < m; i++) cin >> b[i];
  sort(a, a + n);
  sort(b, b + m, [](long long a, long long b) -> bool { return a > b; });
  for (i = 0; i < min(n, m) && a[i] < b[i]; i++) ans += b[i] - a[i];
  cout << ans << '\n';
  return;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  solve(1);
  return 0;
}
