#include <iostream>

using namespace std;

int main(int argc, const char* argv[])
{
	int n;
	string S, T;
	cin >> n >> S >> T;
	int cnt = 0;
	for (int i = 0; i < n; i++) {
		cnt += S[i] != T[i];
	}
	cout << cnt << endl;
	return 0;
}