import heapq
import bisect
N,M = map(int, input().split())
A = [-10**12]+list(map(int, input().split()))+[10**12]
B = list(map(int, input().split()))
SB = set()
d = []
for i in range(M):
    b = B[i]
    j = bisect.bisect(A,b)
    if A[j]-b>b-A[j-1]:
        heapq.heappush(d,(b-A[j-1],i))
    else:
        heapq.heappush(d,(A[j]-b,i))
ans = 0
while len(d):
    v,i = heapq.heappop(d)
    if not i in SB:
        ans+=v
        SB.add(i)
        if i>0 and not i-1 in SB:
            heapq.heappush(d,(B[i]-B[i-1],i-1))
        if i<M-1 and not i+1 in SB:
            heapq.heappush(d,(B[i+1]-B[i],i+1))
print(ans)