import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.TreeSet;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int n = Integer.parseInt(sa[0]);
		int m = Integer.parseInt(sa[1]);
		sa = br.readLine().split(" ");
		TreeSet<Long> set = new TreeSet<>();
		for (int i = 0; i < n; i++) {
			set.add(Long.parseLong(sa[i]));
		}
		sa = br.readLine().split(" ");
		long[] b = new long[m];
		for (int i = 0; i < m; i++) {
			b[i] = Long.parseLong(sa[i]);
		}
		br.close();

		long inf = 2000000007;
		set.add(-inf);
		set.add(inf);
		long[] dp1 = new long[m];
		long[] dp2 = new long[m];
		for (int i = 0; i < m; i++) {
			long v1 = b[i] - set.floor(b[i]);
			if (i > 0) {
				dp1[i] = dp1[i - 1];
				v1 = Math.min(v1, b[i] - b[i - 1]);
			}
			dp1[i] += v1;

			long v2 = set.ceiling(b[i]) - b[i];
			dp2[i] += v2;
			if (i > 0) {
				dp2[i] += dp1[i - 1];
				if (set.ceiling(b[i - 1]) == set.ceiling(b[i])) {
					dp2[i] = Math.min(dp2[i], dp2[i - 1]);
				} else {
					dp1[i] = Math.min(dp1[i], dp2[i - 1] + v1);
					dp2[i] = Math.min(dp2[i], dp2[i - 1] + v2);
				}
			}
		}
//		System.out.println(Arrays.toString(dp1));
//		System.out.println(Arrays.toString(dp2));
		System.out.println(Math.min(dp1[m - 1], dp2[m - 1]));
	}
}