import sys
from heapq import heappush, heappop, heapify

input = sys.stdin.buffer.readline
N, M = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

G = [[] for _ in range(N + M + 1)]
S = [(x, 1) for x in A] + [(x, 0) for x in B]
S.sort()
for i, (x, c) in enumerate(S, 1):
    if c:
        G[0].append((i, 0))
        G[i].append((0, 0))
for i in range(1, N + M):
    G[i].append((i + 1, S[i][0] - S[i - 1][0]))
    G[i + 1].append((i, S[i][0] - S[i - 1][0]))

# https://tjkendev.github.io/procon-library/python/graph/min_st_prim.html
used = [0] * (N + M + 1)
que = [(c, w) for w, c in G[0]]
used[0] = 1
heapify(que)

ans = 0
while que:
    cv, v = heappop(que)
    if used[v]:
        continue
    used[v] = 1
    ans += cv
    for w, c in G[v]:
        if used[w]:
            continue
        heappush(que, (c, w))
print(ans)