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

public class No00000224_Main {

	public static void main(String[] args) throws IOException {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		int n = Integer.parseInt(br.readLine());
		String s = br.readLine();
		String t = br.readLine();

		int cnt = 0;
		for(int i = 0; i < n; i++) {
			if(s.charAt(i) != t.charAt(i))  cnt++;
		}
		System.out.println(cnt);
	}
}