#include <bits/stdc++.h>
using namespace std;
int n;
string a, b;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> a >> b;
  int ans = 0;
  for (int i = 0, j = n - 1; i <= j; ++i, --j) {
    if (i == j) {
      if (a[i] != b[j]) ans++;
      continue;
    }
    if (a[i] == a[j] && b[i] == b[j] && i != j) continue;
    if (b[i] == b[j] && a[i] != b[j]) {
      ans++;
      continue;
    }
    multiset<char> al{a[i], a[j]}, bl{b[i], b[j]};
    multiset<char> diff;
    set_difference(al.begin(), al.end(), bl.begin(), bl.end(),
                   inserter(diff, diff.end()));
    ans += diff.size();
  }
  cout << ans << endl;
}
