import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) throws Exception {
        // Here your code !
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String n = br.readLine();
        String S = br.readLine();
        String T = br.readLine();
                
        Integer convertCount = 0;
        
        if (!S.equals(T)) {
            for (int i = 0; i < Integer.parseInt(n); i++) {
                if (S.charAt(i) != T.charAt(i)) convertCount++;;
            }
        }
        System.out.println(convertCount);
    }
}