#include <bits/stdc++.h>
using namespace std;
string s1, s2;
int main() {
  int n, i, j;
  scanf("%d", &n);
  cin >> s1 >> s2;
  int ans = 0;
  for (i = 0; i < (n / 2); i++) {
    j = n - i - 1;
    map<char, int> mp;
    mp[s1[i]]++;
    mp[s1[j]]++;
    mp[s2[i]]++;
    mp[s2[j]]++;
    int len = mp.size();
    if (len == 4)
      ans += 2;
    else if (len == 3)
      ans += 1 + (s1[i] == s1[j]);
    else if (len == 2)
      ans += (mp[s1[i]] != 2);
  }
  if ((n % 2) && (s1[n / 2] != s2[n / 2])) ans++;
  printf("%d", ans);
  return 0;
}
