import scala.collection.mutable
import scala.collection.mutable.ArrayBuffer
import scala.io.StdIn.*
import scala.util.chaining.*
import scala.math.*

class UnionFind(val size: Int):
  private val vec = Array.fill(size){-1}
  def find(a: Int): Int =
    if vec(a) < 0 then
      a
    else
      vec(a) = find(vec(a))
      vec(a)
  def same(a: Int, b: Int): Boolean = find(a) == find(b)
  def unite(a: Int, b: Int): Unit =
    val i = find(a)
    val j = find(b)
    if i != j then
      if vec(i) < vec(j) then
        vec(i) += vec(j)
        vec(j) = i
      else
        vec(j) += vec(i)
        vec(i) = j
@main def main =
  val Array(n, m) = readLine().split(' ').map(_.toInt)
  val a = readLine().split(' ').map(_.toInt)
  val b = readLine().split(' ').map(_.toInt)
  val allCell = Array.fill(n + m){0}
  val isRed = Array.fill(n + m){false}
  {
    var ai = 0
    var bi = 0
    for i <- 0 until n + m do
      if bi == m || (ai != n && a(ai) < b(bi)) then
        allCell(i) = a(ai)
        isRed(i) = true
        ai += 1
      else
        allCell(i) = b(bi)
        bi += 1
  }
  val uft = UnionFind(n + m + 1)
  for i <- 0 until n + m if isRed(i) do
    uft.unite(i, n + m)
  var result = 0
  for i <- (1 until n + m).sortBy(i => allCell(i) - allCell(i - 1)) do
    if !uft.same(i, i - 1) then
      result += allCell(i) - allCell(i - 1)
      uft.unite(i, i - 1)
  println(result)