#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long i, j, k, n, m, ans = 0;
  string a, b;
  cin >> n >> a >> b;
  for (i = 0; i < n / 2; i++) {
    int j = n - i - 1;
    if (a[i] == b[i] && a[j] == b[j])
      continue;
    else if (a[i] == b[i] && a[j] != b[j])
      ans++;
    else if (a[i] != b[i] && a[j] == b[j])
      ans++;
    else {
      set<char> se({a[i], b[i], a[j], b[j]});
      if (se.size() == 4)
        ans += 2;
      else if (se.size() == 3) {
        ans++;
        if (a[i] == a[j]) ans++;
      }
    }
  }
  if (n % 2 == 1) ans += (a[n / 2] != b[n / 2]);
  cout << ans;
  return 0;
}
