import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    String S = sc.next();
    String T = sc.next();
    int ans = 0;
    for(int i = 0; i < n; i++) {
      char c1 = S.charAt(i);
      char c2 = T.charAt(i);
      if(c1 != c2) ans++;
    }
    System.out.println(ans);
  }
}