#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;   }   