import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        char[] s = sc.next().toCharArray();
        char[] t = sc.next().toCharArray();
        int count = 0;
        for (int i = 0; i < n; i++) {
            if (s[i] != t[i]) {
                count++;
            }
        }
        System.out.println(count);
    }
}