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

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