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());
        }
        int prev = -1;
        PriorityQueue<Bridge> bridges = new PriorityQueue<>();
        for (int i = 1; i <= m; i++) {
            int x = sc.nextInt();
            if (reds.first() <= x) {
                bridges.add(new Bridge(i, 0, x - reds.floor(x)));
            }
            if (reds.last() >= x) {
                bridges.add(new Bridge(i, 0, reds.ceiling(x) - x));
            }
            if (i > 1) {
                bridges.add(new Bridge(i, i - 1, x - prev));
            }
            prev = x;
        }
        UnionFindTree uft = new UnionFindTree(m + 1);
        long ans = 0;
        while (bridges.size() > 0) {
            ans += uft.unite(bridges.poll());
        }
        System.out.println(ans);
    }
    
    static class Bridge implements Comparable<Bridge> {
        int left;
        int right;
        int value;
        
        public Bridge(int left, int right, int value) {
            this.left = left;
            this.right = right;
            this.value = value;
        }
        
        public int compareTo(Bridge 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 (x == parents[x]) {
                return x;
            } else {
                return parents[x] = find(parents[x]);
            }
        }
        
        public int unite(Bridge b) {
            int x = find(b.left);
            int y = find(b.right);
            if (x == y) {
                return 0;
            } else {
                parents[x] = y;
                return b.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();
    }
    
}