#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <iomanip>
#include <cmath>
#include <functional>
using namespace std;
#define diff(x,y) ((x > y) ? (x - y) : (y - x))
#define us(x) (x > 0) ? x : x * -1
#define lli long long int

int main() {
	int n, ans = 0;
	string str, t;
	cin >> n >> str >> t;
	for (int i = 0; i < n; i++) {
		if (str[i] != t[i])	ans++;
	}
	cout << ans << endl;
	return 0;
}