#include "bits/stdc++.h"

#define REP(i, n) for(decltype(n) i = 0; i < (n); i++)
#define REP2(i, x, n) for(decltype(x) i = (x); i < (n); i++)
#define RREP(i, n) for (decltype(n) i = (n) - 1;i >= 0; i--)

#define ALL(a) (a).begin(),(a).end()
#define SORT(c) sort((c).begin(),(c).end())
#define DESCSORT(c) sort(c.begin(), c.end(), greater<int>())

#define LL long long int
#define LD long double

#define PI 3.14159265358979

#define _CRT_SECURE_NO_WARNINGS

using namespace std;

//================================================
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	int N, ans = 0;
	string S, T;
	cin >> N >> S >> T;

	REP(i, N) {
		if (S[i] != T[i]) {
			ans++;
		}
	}

	cout << ans << "\n";
	return 0;
}