import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        String s = in.next();
        String t = in.next();
        int count = 0;
        char[] s_to_c = s.toCharArray();
        char[] t_to_c = t.toCharArray();

        for(int i=0; i<n; i++) {
            if(s_to_c[i] != t_to_c[i]) {
                count++;
            } else {
                // nothing
            }
        }

        System.out.println(count);

        in.close();
    }
}