# グラフ
# 頂点0を作成し、全ての赤の頂点に対して長さ0の辺を貼る
# 全ての頂点を昇順に並べ、隣合った点に距離を表す辺を貼る
# 最小全域木

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

G = [[] for i in range(N + M + 1)]
for i in range(1, N + 1):
    G[0].append([i, 0])
    G[i].append([0, 0])
    
A = [[A[i], i + 1] for i in range(N)]
B = [[B[i], N + i + 1] for i in range(M)]
AB = A + B
AB = sorted(AB, key = lambda x:x[0])

for i in range(N + M - 1):
    dist = abs(AB[i + 1][0] - AB[i][0])
    to_v = AB[i + 1][1]
    from_v = AB[i][1]
    G[to_v].append([from_v, dist])
    G[from_v].append([to_v, dist])
    
import heapq as hq
q = []
hq.heappush(q, (0, 0))
visited = [False] * (N + M + 1)
ans = 0
while q:
    d, v = hq.heappop(q)
    if visited[v]:
        continue
    visited[v] = True
    ans += d
    for child, dist in G[v]:
        if visited[child]:
            continue
        hq.heappush(q, (dist, child))
        
print(ans)