import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

import static java.lang.System.in;


public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        int n = Integer.parseInt(reader.readLine());
        String S = reader.readLine();
        String T = reader.readLine();
        int changeCounter = 0;
        for (int i = 0; i < n; i++) {
            if(S.charAt(i)!=T.charAt(i)) {
                changeCounter+=1;
            }
        }
        System.out.println(changeCounter);
    }
}