object Main extends App {
  import scala.io.StdIn._

  val n = readInt
  val s = readLine.trim
  val t = readLine.trim
  val sCounts = ('a' to 'z').map(c ⇒ s.count(_ == c)).sorted
  val tCounts = ('a' to 'z').map(c ⇒ t.count(_ == c)).sorted
  println(
    sCounts.zip(tCounts).map{case (a, b) ⇒ math.abs(a - b)}.sum / 2
  )
}
