import java.util.*;
import java.math.*;
import java.text.*;

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