import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;
import java.util.TreeSet;

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