#include <iostream>
#include <sstream>
#include <math.h>
#include <stack>
#include <set>
#include <algorithm>
#include <string>
#include <queue>
#include <stack>
#include <map>
#include <cstdio>
#include <vector>
using namespace std;

#define INF (1 << 30)
#define INFLL (1LL << 60)

int main() {
	string str1,str2;
	int n,ans = 0;
	cin >> n;
	cin >> str1 >> str2;
	for(int i = 0;i < n;i++){
		if(str1[i] != str2[i]) ans++;
	}
	cout << ans << endl;
	return 0;
}