#include <bits/stdc++.h>
using namespace std;
const int N = 100200;
int n;
string a, b;
int count(initializer_list<char> l) {
  map<char, int> fr;
  vector<int> v(l.begin(), l.end());
  int mx = 0;
  for (auto i : l) {
    ++fr[i];
    mx = max(fr[i], mx);
  }
  int ans = 0;
  if (fr.size() == 4 or (fr.size() == 3 and v[0] == v[1]))
    ans += 2;
  else if (fr.size() == 3)
    ++ans;
  else if (fr.size() == 2 and mx == 3)
    ++ans;
  return ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> a >> b;
  int ans = 0;
  if (n & 1) ans += (a[n / 2] != b[n / 2]);
  for (int i = 0; i < n / 2; ++i)
    ans += count({a[i], a[n - i - 1], b[i], b[n - i - 1]});
  cout << ans << endl;
  return 0;
}
