n,m = map(int,input().split())
a = [-(10**9 + 1)] + list(map(int,input().split())) + [2*10**9 + 1] 
b = list(map(int,input().split()))
ab = []
for i in range(n+2):
    ab.append([a[i],1])
for i in range(m):
    ab.append([b[i],0])
ab.sort()
flg = 1
max_ = 0
sum_ = 0
ans = 0
for i in range(n+m+2):
    idx,color = ab[i]
    if color == 1 and flg == 0:
        max_ = max(ab[i][0] - ab[i-1][0] ,max_)
        sum_ += ab[i][0] - ab[i-1][0]
        ans += sum_ - max_
    elif color == 0 and flg == 1:
        max_ = ab[i][0] - ab[i-1][0]
        sum_ = ab[i][0] - ab[i-1][0]
    elif color == 0 and flg == 0:
        max_ = max(ab[i][0] - ab[i-1][0] ,max_)
        sum_ += ab[i][0] - ab[i-1][0]
    flg = color
    
print(ans)