import java.util.Scanner;


public class Main_yukicoder224 {

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

        int n = sc.nextInt();
        char[] s = sc.next().toCharArray();
        char[] t = sc.next().toCharArray();

        int ret = 0;
        for (int i = 0; i < n; i++) {
        	if (s[i] != t[i]) {
        		ret++;
        	}
        }
        
        System.out.println(ret);
        
        sc.close();
    }
}