#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, ans = 0, i, j;
  string a, b;
  char p, q, r, s;
  cin >> n >> a >> b;
  for (i = 0, j = n - 1; i < j; i++, j--) {
    p = min(a[i], a[j]), q = max(a[i], a[j]), r = min(b[i], b[j]),
    s = max(b[i], b[j]);
    if (p == q) {
      if (r != s) {
        if (p == r || p == s)
          ans++;
        else
          ans += 2;
      }
    } else {
      if (r == s) {
        ans++;
      } else {
        ans += 2;
        if (p == r || p == s) ans--;
        if (q == r || q == s) ans--;
      }
    }
  }
  if (i == j) {
    if (a[i] != b[i]) ans++;
  }
  cout << ans;
}
