import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		String S = sc.next(), T = sc.next();
		
		char[] charS = S.toCharArray(), charT = T.toCharArray();
		
		int cnt = 0;
		
		for(int i = 0; i < n; i++) {
			if(charS[i] != charT[i]) {
				cnt++;
			}
		}
		
		System.out.println(cnt);
	}
}