#include <stdio.h>
#include <stdlib.h>

typedef struct {
	int key, id;
} data;

void merge_sort(int n, data x[])
{
	static data y[400001] = {};
	if (n <= 1) return;
	merge_sort(n / 2, &(x[0]));
	merge_sort((n + 1) / 2, &(x[n/2]));
	
	int i, p, q;
	for (i = 0, p = 0, q = n / 2; i < n; i++) {
		if (p >= n / 2) y[i] = x[q++];
		else if (q >= n) y[i] = x[p++];
		else y[i] = (x[p].key < x[q].key)? x[p++]: x[q++];
	}
	for (i = 0; i < n; i++) x[i] = y[i];
}

typedef struct {
	data obj[400001];
	int size;
} min_heap;

void push(min_heap* h, data x)
{
	int i = ++(h->size), j = i >> 1;
	data tmp;
	h->obj[i] = x;
	while (j > 0) {
		if (h->obj[i].key < h->obj[j].key) {
			tmp = h->obj[j];
			h->obj[j] = h->obj[i];
			h->obj[i] = tmp;
			i = j;
			j >>= 1;
		} else break;
	}
}

data pop(min_heap* h)
{
	int i = 1, j = 2;
	data output = h->obj[1], tmp;
	h->obj[1] = h->obj[(h->size)--];
	while (j <= h->size) {
		if (j < h->size && h->obj[j^1].key < h->obj[j].key) j ^= 1;
		if (h->obj[j].key < h->obj[i].key) {
			tmp = h->obj[j];
			h->obj[j] = h->obj[i];
			h->obj[i] = tmp;
			i = j;
			j <<= 1;
		} else break;
	}
	return output;
}

typedef struct {
	int *par, *size;
} UF_forest;

void UF_initialize(UF_forest *F, int n)
{
	int i;
	F->par = (int*)malloc(sizeof(int) * (n + 1));
	F->size = (int*)malloc(sizeof(int) * (n + 1));
	for (i = 1; i <= n; i++) {
		F->par[i] = i;
		F->size[i] = 1;
	}
}

int UF_root(UF_forest *F, int v)
{
	if (F->par[v] == v) return v;
	else {
		F->par[v] = UF_root(F, F->par[v]);
		return F->par[v];
	}
}

void UF_merge(UF_forest *F, int u, int v)
{
	u = UF_root(F, u);
	v = UF_root(F, v);
	if (u == v) return;
	else if (F->size[u] > F->size[v]) {
		F->par[v] = u;
		F->size[u] += F->size[v];
	} else {
		F->par[u] = v;
		F->size[v] += F->size[u];
	}
}

int main()
{
	int i, N, M;
	data d[400001];
	scanf("%d %d", &N, &M);
	for (i = 0; i < N; i++) {
		scanf("%d", &(d[i].key));
		d[i].id = 1;
	}
	for (i = N; i < N + M; i++) {
		scanf("%d", &(d[i].key));
		d[i].id = -1;
	}
	merge_sort(N + M, d);

	int r = -1, ans = 0;
	min_heap h;
	data e;
	UF_forest F;
	h.size = 0;
	UF_initialize(&F, N + M);
	for (i = 0; i < N + M; i++) {
		if (d[i].id > 0) {
			if (r < 0) r = i + 1;
			else UF_merge(&F, i + 1, r);
		}
	}
	for (i = 1; i < N + M; i++) {
		if (d[i-1].id > 0 && d[i].id > 0) continue;
		e.key = d[i].key - d[i-1].key;
		e.id = i;
		push(&h, e);
	}
	while (h.size > 0) {
		e = pop(&h);
		if (UF_root(&F, e.id) != UF_root(&F, e.id + 1)) {
			UF_merge(&F, e.id, e.id + 1);
			ans += e.key;
		}
	}
	printf("%d\n", ans);
	fflush(stdout);
	return 0;
}