//inlclude前用define 
#define _USE_MATH_DEFINES

//include
#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<cmath>

using namespace std;
//typedef
typedef vector<int> VI;
typedef vector<string> VS;
typedef vector<char> VC;

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