import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone{
    public static void main(String[] args) throws Exception{
        // your code goes here
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        String s = br.readLine();
        String t = br.readLine();
        
        int ans = 0;
        for(int i=0;i<n;i++){
            if(s.charAt(i) != t.charAt(i)){
                ans++;
            }
        }
        System.out.println(ans);
    }
}