from scipy.sparse.csgraph import minimum_spanning_tree
from scipy.sparse import csr_matrix

N, M = map(int, input().split())
A = map(int, input().split())
B = map(int, input().split())
nodes = []
for i, a in enumerate(A):
    nodes.append((a, i))
for i, b in enumerate(B, N):
    nodes.append((b, i))
nodes.sort()

length = [0] * N
frm = list(range(N))
to = [N + M] * N

for i in range(N + M - 1):
    frm.append(nodes[i][1])
    to.append(nodes[i + 1][1])
    length.append(nodes[i + 1][0] - nodes[i][0])

matr = csr_matrix((length, (frm, to)), shape=(N + M + 1, N + M + 1))
T = minimum_spanning_tree(matr).astype(int)
print(T.sum())