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

int main(){
	int n, count = 0;
	string s, t;

	cin >> n >> s >> t;

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