import java.util.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		int n = sc.nextInt();
		char[] s = sc.next().toCharArray();
		char[] t = sc.next().toCharArray();
		int times = 0;
		for (int i=0; i<s.length; i++) {
			if (s[i]!=t[i]) {times++;}
		}
		System.out.println(times);
	}
}