import java.util.Scanner

object Problem224 {

  def proc(S: String, T: String): Int = {
    S.zip(T).count(p => p._1 != p._2)
  }

  def main(args: Array[String]) = {
    val sc = new Scanner(System.in)
    val n = sc.nextInt()
    val S = sc.next()
    val T = sc.next()

    val result = proc(S, T)
    println(result)
  }
}