import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int m = sc.nextInt();
        Field[] fields = new Field[n + m];
        for (int i = 0; i < n; i++) {
            fields[i] = new Field(true, sc.nextInt());
        }
        for (int i = n; i < n + m; i++) {
            fields[i] = new Field(false, sc.nextInt());
        }
        Arrays.sort(fields);
        UnionFindTree uft = new UnionFindTree(n + m + 1);
        ArrayList<Path> list = new ArrayList<>();
        for (int i = 0; i < n + m - 1; i++) {
            if (fields[i].isRed) {
                uft.unite(i, n + m);
            }
            list.add(new Path(i, i + 1, fields[i + 1].value - fields[i].value));
        }
        if (fields[n + m - 1].isRed) {
            uft.unite(n + m - 1, n + m);
        }
        Collections.sort(list);
        long ans = 0;
        for (Path p : list) {
            if (!uft.same(p)) {
                uft.unite(p);
                ans += p.value;
            }
        }
        System.out.println(ans);
    }
    
    static class Field implements Comparable<Field> {
        boolean isRed;
        int value;
        
        public Field(boolean isRed, int value) {
            this.isRed = isRed;
            this.value = value;
        }
        
        public int compareTo(Field another) {
            return value - another.value;
        }
    }
    
    static class Path implements Comparable<Path> {
        int left;
        int right;
        int value;
        
        public Path(int left, int right, int value) {
            this.left = left;
            this.right = right;
            this.value = value;
        }
        
        public int compareTo(Path another) {
            return value - another.value;
        }
    }
    
    static class UnionFindTree {
        int[] parents;
        
        public UnionFindTree(int size) {
            parents = new int[size];
            for (int i = 0; i < size; i++) {
                parents[i] = i;
            }
        }
        
        public int find(int x) {
            if (parents[x] == x) {
                return x;
            } else {
                return parents[x] = find(parents[x]);
            }
        }
        
        public boolean same(int x, int y) {
            return find(x) == find(y);
        }
        
        public boolean same(Path p) {
            return same(p.left, p.right);
        }
        
        public void unite(int x, int y) {
            if (!same(x, y)) {
                parents[find(x)] = find(y);
            }
        }
        
        public void unite(Path p) {
            unite(p.left, p.right);
        }
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}