#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <string>
#include <stdio.h>

using namespace std;

int main() {

	int n;
	string s, t;
	cin >> n >> s >> t;

	int cnt = 0;
	for (int i = 0; i < n; i++) {
		if (s[i] != t[i]) cnt++;
	}

	cout << cnt << endl;

	return 0;
}