#include<iostream>
using namespace std;
int main(void)
{
	int n, i, count = 0;
	char s[1010], t[1010];

	cin >> n >> s >> t;
	for (i = 0; i < n; i++) {
		if (s[i] != t[i])
			count++;
	}
	cout << count << endl;

	return 0;
}