import itertools as iter
import collections as coll
import heapq as hq
import bisect as bis
from decimal import Decimal as dec
from copy import deepcopy as dcopy
import math
import sys
sys.setrecursionlimit(10**6)
def input():
    return sys.stdin.readline().rstrip()
def getN():
	return int(sys.stdin.readline())
def getNs():
	return map(int,sys.stdin.readline().split())
def getList():
	return list(map(int,sys.stdin.readline().split()))
def strinps(n):
	return [sys.stdin.readline().rstrip() for _ in range(n)]
pi = 3.141592653589793
mod = 10**9+7
MOD = 998244353
INF = math.inf
dx = [1,0,-1,0];	dy = [0,1,0,-1]

"""
Union-Find
from : https://github.com/customaddone/beginPython/blob/master/cgi-bin/library/unionfind/unionfind.py
ref : https://algo-logic.info/union-find-tree/
"""

class UnionFind():
	#Uni = UnionFind(n) のようにする
	def __init__(self, n):
		self.n = n
		self.parents = [-1] * n

	#xの親（親がいないときは自身の番号を返す）
	def find(self, x):
		if self.parents[x] < 0:
			return x
		else:
			self.parents[x] = self.find(self.parents[x])
			return self.parents[x]

	#xとyを関係付ける
	def union(self, x, y):
		x = self.find(x)
		y = self.find(y)

		if x == y:
			return

		if self.parents[x] > self.parents[y]:
			x, y = y, x
		# if x > y: # よりrootのインデックスが小さい方が親
			# x, y = y, x

		self.parents[x] += self.parents[y]
		self.parents[y] = x

	#xとyが同じ組に属するかどうか
	def same(self, x, y):
		return self.find(x) == self.find(y)

	#xが属する組の大きさ
	def size(self, x):
		return -self.parents[self.find(x)]

	#xが属する組の全要素をリストとして取得
	def members(self, x):
		root = self.find(x)
		return [i for i in range(self.n) if self.find(i) == root]

	#Union-Find木の根に当たる要素全てをリストとして取得
	def roots(self):
		return [i for i, x in enumerate(self.parents) if x < 0]

	#Union-Find木の根とそれに属する組の全要素
	def all_group_members(self):
		return {r: self.members(r) for r in self.roots()}

"""
Main Code
"""

n,m = getNs()
a = [i - 1 for i in getNs()]
b = [i - 1 for i in getNs()]
rb = max(a[-1],b[-1]) + 1

uni = UnionFind(n + m + 1)
route = []
x = sorted(a + b)
st = set(a)
for i in range(n + m):
	if(x[i] in a):
		route.append((0, i, n + m))
for i in range(n + m - 1):
	route.append((x[i + 1] - x[i], i, i + 1))
route.sort()

ans = 0
for c,s,t in route:
	if(uni.size(0) == n + m + 1):
		break
	if(uni.same(s,t)):
		continue
	uni.union(s,t)
	ans += c
print(ans)