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

public class No224 {
    public static void main(String[] args) {
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(
                    System.in));
            int N = Integer.parseInt(br.readLine());
            char[] S = br.readLine().toCharArray();
            char[] T = br.readLine().toCharArray();
            int count = 0;
            for (int i = 0; i < N; i++) {
                if (S[i] != T[i])
                    count++;
            }

            System.out.println(count);
        } catch (Exception e) {
            System.err.println("Error:" + e.getMessage());
        }
    }
}