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

class DSU:
    def __init__(self, n):
        self._n = n
        self.parent_or_size = [-1] * n

    def merge(self, a, b):
        assert 0 <= a < self._n
        assert 0 <= b < self._n
        x, y = self.leader(a), self.leader(b)
        if x == y: return x
        if -self.parent_or_size[x] < -self.parent_or_size[y]: x, y = y, x
        self.parent_or_size[x] += self.parent_or_size[y]
        self.parent_or_size[y] = x
        return x

    def same(self, a, b):
        assert 0 <= a < self._n
        assert 0 <= b < self._n
        return self.leader(a) == self.leader(b)

    def leader(self, a):
        assert 0 <= a < self._n
        if self.parent_or_size[a] < 0: return a
        self.parent_or_size[a] = self.leader(self.parent_or_size[a])
        return self.parent_or_size[a]

    def size(self, a):
        assert 0 <= a < self._n
        return -self.parent_or_size[self.leader(a)]

    def groups(self):
        leader_buf = [self.leader(i) for i in range(self._n)]
        result = [[] for _ in range(self._n)]
        for i in range(self._n): result[leader_buf[i]].append(i)
        return [r for r in result if r != []]

X = A+B
X.sort()
SA = set(A)
ans = 0
d = DSU(N+M+1)
for i in range(N+M):
    if X[i] in SA:
        d.merge(i,N+M)

edges = [(X[i+1]-X[i],i) for i in range(N+M-1)]
edges.sort()
for i in range(N+M-1):
    c,x = edges[i]
    if d.same(x,x+1):
        continue
    ans += c
    d.merge(x,x+1)
print(ans)