import sys
input = sys.stdin.readline
def iinput(): return int(input())
def sinput(): return input().rstrip()
def i0input(): return int(input()) - 1
def linput(): return list(input().split())
def liinput(): return list(map(int, input().split()))
def miinput(): return map(int, input().split())
def li0input(): return list(map(lambda x: int(x) - 1, input().split()))
def mi0input(): return map(lambda x: int(x) - 1, input().split())
INF = 10**20
MOD = 1000000007

from bisect import bisect_left

N, M = liinput()
A = liinput()
B = liinput()
ans = 0
if A[0] > B[0]:
    ans += A[0] - B[0]
if A[-1] < B[-1]:
    ans += B[-1] - A[-1]
if N == 1:
    print(ans)
    exit()

for a1, a2 in zip(A[:-1], A[1:]):
    idx1 = bisect_left(B, a1)
    idx2 = bisect_left(B, a2)
    m = INF
    tmp = [a1]
    for i in range(idx1, idx2):
        tmp.append(B[i])
    tmp.append(a2)
    for b1, b2 in zip(tmp[:-1], tmp[1:]):
        m = min(m, b1 - a1 + a2 - b2)
    ans += m
print(ans)