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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int m = sc.nextInt();
        TreeSet<Integer> reds = new TreeSet<>();
        for (int i = 0; i < n; i++) {
            reds.add(sc.nextInt());
        }
        reds.add(-Integer.MIN_VALUE / 2);
        reds.add(Integer.MAX_VALUE);
        PriorityQueue<Path> queue = new PriorityQueue<>();
        int[] blues = new int[m + 2];
        for (int i = 1; i <= m; i++) {
            blues[i] = sc.nextInt();
            queue.add(new Path(i, blues[i] - reds.floor(blues[i])));
            queue.add(new Path(i, reds.ceiling(blues[i]) - blues[i]));
        }
        blues[0] = -Integer.MIN_VALUE / 2;
        blues[m + 1] = Integer.MAX_VALUE;
        HashSet<Integer> used = new HashSet<>();
        long ans = 0;
        while (queue.size() > 0) {
            Path p = queue.poll();
            if (p.idx >= 1 && p.idx <= m && !used.contains(p.idx)) {
                ans += p.value;
                queue.add(new Path(p.idx - 1, blues[p.idx] - blues[p.idx - 1]));
                queue.add(new Path(p.idx + 1, blues[p.idx + 1] - blues[p.idx]));
                used.add(p.idx);
            }
        }
        System.out.println(ans);
    }
    
    static class Path implements Comparable<Path> {
        int idx;
        int value;
        
        public Path(int idx, int value) {
            this.idx = idx;
            this.value = value;
        }
        
        public int compareTo(Path another) {
            return value - another.value;
        }
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    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 int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}