#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
using namespace std;
typedef long long LL;
typedef vector<int> VI;

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