#include <bits/stdc++.h>
using namespace std;
int n;
string s1, s2;
int cnt = 0;
int a[127], b[127];
int main() {
  cin >> n;
  cin >> s1 >> s2;
  for (int i = 0; i < n / 2; i++) {
    if (s2[i] != s2[n - 1 - i]) {
      char c1 = s2[i], c2 = s2[n - 1 - i];
      a[s1[i]] = a[s1[n - 1 - i]] = b[c1] = b[c2] = true;
      if (!a[c1]) cnt++;
      if (!a[c2]) cnt++;
      a[s1[i]] = a[s1[n - 1 - i]] = b[c1] = b[c2] = false;
    } else {
      if (s1[i] != s1[n - 1 - i]) cnt++;
    }
  }
  if (n % 2 == 1) {
    if (s1[n / 2] != s2[n / 2]) cnt++;
  }
  cout << cnt << '\n';
  return 0;
}
