#include <iostream>
#include <string>
using namespace std;

int main(){
	int n;
	int cnt = 0;
	string s;
	string t;
	cin >> n;
	cin >> s;
	cin >> t;
	for (int i = 0; i < n; i++){
		char a = s.at(i);
		char b = t.at(i);
		if (a != b){
			cnt += 1;
		}
	}
	cout << cnt << endl;

	return 0;
}