#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5 + 5;
const int mod = 1e9 + 9;
int Case = 1, n, m;
int cc[maxn];
long long sum[maxn];
int check(char ch1, char ch2, char ch3, char ch4) {
  char ch[] = {ch1, ch2, ch3, ch4};
  char zz[] = {ch1, ch2, ch3, ch4};
  sort(zz, zz + 4);
  sort(ch, ch + 4);
  int num = unique(ch, ch + 4) - ch;
  if (num == 4) return 2;
  if (num == 3) {
    if (ch1 == ch2) return 2;
    return 1;
  }
  if (num == 2) {
    if (zz[1] != zz[2]) return 0;
    return 1;
  }
  if (num == 1) return 0;
}
char aa[maxn], bb[maxn];
void solve() {
  scanf("%d", &n);
  scanf("%s%s", aa + 1, bb + 1);
  int res = 0;
  for (int i = 1; i <= n / 2; i++) {
    res += check(aa[i], aa[n + 1 - i], bb[i], bb[n + 1 - i]);
  }
  if (n & 1) {
    if (aa[(n + 1) / 2] != bb[(n + 1) / 2]) ++res;
  }
  printf("%d\n", res);
}
int main() {
  ios::sync_with_stdio(false);
  while (Case--) {
    solve();
  }
  return 0;
}
