#include <bits/stdc++.h>
using namespace std;
int n;
string s1, s2;
vector<char> cur;
int check(char a, char b, char c, char d) {
  cur.clear();
  cur.push_back(a);
  cur.push_back(b);
  cur.push_back(c);
  cur.push_back(d);
  sort(cur.begin(), cur.end());
  if (cur[0] == cur[3] || cur[0] == cur[1] && cur[2] == cur[3]) {
    return 0;
  }
  int h2 = 0;
  if (cur[0] == cur[1] || cur[1] == cur[2] || cur[2] == cur[3]) h2 = 1;
  if (!h2) {
    return 2;
  }
  if (c != d && a == b && c != a && d != a) {
    return 2;
  }
  return 1;
}
int main() {
  srand(time(NULL));
  cin >> n;
  cin >> s1 >> s2;
  int res = 0;
  for (int i = 0; i <= n - (i + 1); i++) {
    int l = i;
    int r = n - (i + 1);
    if (l == r) {
      if (s1[l] != s2[r]) res++;
    } else {
      res += check(s1[l], s1[r], s2[l], s2[r]);
    }
  }
  cout << res << endl;
  return 0;
}
