import java.util.*;

public class Exercise72{
  public static void main (String[] args){

    Scanner sc = new Scanner(System.in);

    int n = sc.nextInt();

    String s = sc.next();
    String t = sc.next();

    char[] sArray = s.toCharArray();
    char[] tArray = t.toCharArray();

    int count = 0;

    for(int i = 0; i < n; i++){
      if(sArray[i] != tArray[i]){
        count++;
      }
    }
    System.out.println(count);
  }
}