#include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     long long i, j, k, n, m, ans = 0;     string a, b;     cin >> n >> a >> b;     for (i = 0; i < n / 2; i++) {       int j = n - i - 1;       if (a[i] == b[i] && a[j] == b[j])         continue;       else if (a[i] == b[i] && a[j] != b[j])         ans++;       else if (a[i] != b[i] && a[j] == b[j])         ans++;       else {         set<char> se({a[i], b[i], a[j], b[j]});         if (se.size() == 4)           ans += 2;         else if (se.size() == 3) {           ans++;           if (a[i] == a[j]) ans++;         }       }     }     if (n % 2 == 1) ans += (a[n / 2] != b[n / 2]);     cout << ans;     return 0;   }   