#include <math.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, l, n) for (int i = (l); i < (n); i++)
#define all(x) x.begin(), x.end()
#define lb lower_bound
#define ub upper_bound
#define lbi(A, x) (ll)(lb(all(A), x) - A.begin())
#define ubi(A, x) (ll)(ub(all(A), x) - A.begin())
using ll = long long;
using Pair = pair<int, int>;
template <class T>	using V = vector<T>;
template <class T>	using VV = V<V<T> >;
const ll INF = 1000000000000000001;
const int inf = 1001001001;
const ll mod = 1000000007;
const ll MOD = 998244353;
template <class T>  inline V<T> getList(int n) { V<T> res(n); rep(i, 0, n) { cin >> res[i]; }return res; }
template <class T>  inline VV<T> getGrid(int m, int n) { VV<T> res(m, V<T>(n)); rep(i, 0, m) { res[i] = getList<T>(n); }return res; }
inline V<int> dtois(string& s) { V<int> vec = {}; for (auto& e : s) { vec.push_back(e - '0'); } return vec; }


int main(void) {
	int n, m;	cin >> n >> m;
	V<int> a = getList<int>(n);
	V<int> b = getList<int>(m);

	dsu uni(n + m + 1);
	VV<int> route = {};
	set<int> st = {};
	V<int> x = {};
	for (auto& i : a) {
		st.insert(i);
		x.push_back(i);
	}
	for (auto& i : b) {
		x.push_back(i);
	}
	sort(all(x));

	rep(i, 0, m + n) {
		if (st.find(x[i]) != st.end()) {
			uni.merge(i, m + n);
		}
	}
	rep(i, 0, m + n - 1) {
		route.push_back({ x[i + 1] - x[i],i,i + 1 });
	}
	sort(all(route));

	ll ans = 0;
	for (auto& l : route) {
		int c = l[0]; int s = l[1]; int t = l[2];
		if (uni.size(0) == n + m + 1) {
			break;
		}
		if (uni.same(s, t)) {
			continue;
		}
		uni.merge(s, t);
		ans += c;
	}

	cout << ans << endl;
	return 0;
}