#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s1, s2;
  cin >> s1 >> s2;
  int flag = 0;
  if (n % 2 != 0) flag = 1;
  int mid;
  if (flag)
    mid = (n + 1) / 2;
  else
    mid = n / 2;
  int cnt = 0;
  for (int i = 0; i < n / 2; i++) {
    int l = i, r = n - i - 1;
    int a[30];
    fill(a, a + 30, 0);
    a[s1[l] - 'a']++;
    a[s1[r] - 'a']++;
    a[s2[l] - 'a']++;
    a[s2[r] - 'a']++;
    int k = 0;
    int b[4];
    int counts = 0;
    for (int j = 0; j < 30; j++) {
      if (a[j]) k++;
      if (a[j]) {
        b[counts++] = a[j];
      }
    }
    sort(b, b + k);
    if (k == 4) {
      cnt += 2;
      continue;
    }
    if (k == 3) {
      if (s1[l] == s1[r])
        cnt += 2;
      else
        cnt++;
    }
    if (k == 2) {
      if (b[1] == 3) {
        cnt++;
      }
    }
  }
  if (flag)
    if (s1[mid - 1] != s2[mid - 1]) cnt++;
  cout << cnt;
}
