import java.util.Scanner;

public class No224 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		String s = sc.next();
		String t = sc.next();
		
		char[] s1 = s.toCharArray();
		char[] t1 = t.toCharArray();
		int count=0;
		
		for(int i=0;i<n;i++){
			if(s1[i] != t1[i])
				count++;
		}
		
		System.out.println(count);
		

	}

}