#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={0,1,-1,0,1,1,-1,-1,0};
const ll dx[9]={1,0,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

struct UnionFind {
    vector<int> par;
    vector<int> edge;
    
    UnionFind(int n) : par(n, -1),edge(n, 0) {}

    int root(int x) {
        if (par[x] < 0) return x;
        else return par[x] = root(par[x]);
    }
    
    bool same(int x, int y) {
        return root(x) == root(y);
    }
    
    bool merge(int x, int y) {
        x = root(x); y = root(y);
        if (x == y) {
            edge[x]++;
            return false;
        }
        if (par[x] > par[y]) swap(x, y);
        par[x] += par[y];
        par[y] = x;
        edge[x] += edge[y]+1;
        return true;
    }
    
    int size(int x) {
        return -par[root(x)];
    }
};
struct edge{
    ll u,v,c;
    bool operator<(edge b){
        return c<b.c;
    }
};
int main(){
    ll n,m;cin >> n >> m;
    vector<pl> v;
    rep(i,n){
        ll a;cin >> a;v.push_back({a,0});
    }
    rep(i,m){
        ll b;cin >> b;v.push_back({b,1});
    }
    sort(all(v));
    UnionFind uf(n+m+1);
    ll s=n+m;
    rep(i,n+m){
        if(v[i].second==0)uf.merge(i,s);
    }
    vector<edge> es;
    rep(i,n+m-1){
        es.push_back({i,i+1,v[i+1].first-v[i].first});
    }
    sort(all(es));
    ll ans=0;
    for(auto [u,v,c]:es){
        if(uf.same(u,v))continue;
        //cout << u <<" " << v <<" " << c << endl;
        ans+=c;uf.merge(u,v);
    }
    cout << ans << endl;
}