#include <iostream>	//cin, cout
#include <vector>	//vector
#include <algorithm> //sort,min,max
#include <string>	//string
#include <ios>		//fixed
#include <iomanip>	//setprecision
#include <utility> //swap
#include <cstdlib>	//abs(int)
#include <cmath>	//sqrt
#include <sstream>	//stringstream,getline
#include <cmath>	//ceil

using namespace std;

int main() {

	int n;
	string S, T;
	cin >> n >> S >> T;

	int ans = 0;
	for (int i = 0; i < n; i++) {
		if (S[i] != T[i]) {
			ans++;
		}
	}

	cout << ans << endl;

	return 0;

}