import java.io.*;
import java.util.*;
import java.math.*;

class Main224 {
	
	public static void out (Object out) {
		System.out.println(out);
	}
	
	public static void main (String[] args) throws IOException {
		BufferedReader br = 
			new BufferedReader(new InputStreamReader(System.in));
		
		int ans = 0;
		int n = Integer.parseInt(br.readLine());
		String s = br.readLine();
		String t = br.readLine();
		
		for (int i = 0; i < n; i++) {
			if (s.charAt(i) != t.charAt(i)) ans++;
		}
		
		out(ans);
		
	}
}