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

public class Main {
	public static void main(String[] args) {
		BufferedReader read = new BufferedReader(new InputStreamReader(System.in));

		try {
			int n = Integer.parseInt(read.readLine());
			String s = read.readLine();
			String t = read.readLine();

			int ans = 0;
			for (int i = 0; i < n; ++i) {
				if (s.charAt(i) != t.charAt(i)) {
					++ans;
				}
			}

			System.out.println(ans);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}