#include <bits/stdc++.h>
using namespace std;
string to_string(string s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto& x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
void debug_out() { cerr << '\n'; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
void solve() {
  int n;
  string a, b;
  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[i]) ans++;
      continue;
    } else if (b[i] == b[j]) {
      if (a[i] == a[j])
        ;
      else
        ans++;
      continue;
    }
    vector<int> isthere(26);
    isthere[b[i] - 'a']++;
    isthere[b[j] - 'a']++;
    if (isthere[a[i] - 'a']) isthere[a[i] - 'a']--;
    if (isthere[a[j] - 'a']) isthere[a[j] - 'a']--;
    42;
    ans += accumulate((isthere).begin(), (isthere).end(), 0);
  }
  cout << ans << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
