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 c = 0;
        for(int i=0; i<n; i++){
            if( S.charAt(i)!=T.charAt(i) ){
                c++;
            }
        }
        System.out.println(c);
    }
}