#include <cstring>
#include <string>
#include <queue>
#include <map>
#include <vector>
#include <algorithm>
#include <iostream>
#include <cstdio>

using namespace std;
typedef unsigned int uint; typedef long long ll; typedef unsigned long long ull;
#define repi(_I, _B, _E) for(int _I = (_B); (_I) < (_E); ++ (_I))
#define rep(_I, _N) for(int _I = 0; (_I) < (_N); ++ (_I))


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

	return 0;
}