N,M = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))

A = [[A[i], True] for i in range(N)]
B = [[B[i], False] for i in range(M)]

AB = sorted(A + B, key = lambda x:x[0])

G = [[] for i in range(N + M)]
import heapq as hq
q = []
for i in range(N + M - 1):
    G[i].append([i + 1, AB[i + 1][0] - AB[i][0]])
    G[i + 1].append([i, AB[i + 1][0] - AB[i][0]])
    if AB[i][1]:
        hq.heappush(q, (0, i))

if AB[N + M - 1][1]:
    hq.heappush(q, (0, N + M - 1))
    
ans = 0
seen = set()
while q:
    d, v = hq.heappop(q)
    if v in seen:
        continue
    seen.add(v)
    ans += d
    for child, cost in G[v]:
        if child in seen:
            continue
        hq.heappush(q, (cost, child))
        
print(ans)