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

public class Main {

	/**
	 * @param args
	 * @throws IOException
	 */
	public static void main(String[] args) throws IOException {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int num = br.read();
		String aaa = br.readLine();
		String bbb = br.readLine();
		int count = 0;
		for (int i = 0; i < num; i++) {
			if (aaa.charAt(i) != bbb.charAt(i)) {
				count += 1;
			}
		}
		System.out.println(count);
	}
}