#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 1010;
int n;
char a[N], b[N];
int main() {
cin >> n >> a >> b;
int ans = 0;
for (int i = 0; i < n; i++) {
if (a[i] == b[i]) continue;
ans++;
while (a[i] != b[i]) i++;
i--;
}
cout << ans << endl;
return 0;
}