import java.util.*;

class No0224{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		String s = sc.next();
		String t = sc.next();
		int cnt = 0;

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