#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
using namespace std;
int n;
int main(){
	string s, t;
	cin >> n >> s >> t;
	int countt = 0;
	for (int i = 0; i < s.size(); i++){
		if (s[i] != t[i]){
			countt++;
		}
	}
	cout << countt << endl;
	return 0;
}