Language: C++

#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define pp pair<pair<ll, ll>,pair<ll, ll>>
#define pll pair<ll,ll>
#define pdd pair<double,double>
#define vii vector<int>
#define vll vector<ll>
#define mat vector<vector<ll>>
#define lb lower_bound
#define pb push_back
#define fi first
#define sc second
#define rep(i,n) for(ll i=0;i<n;i++)
#define rep2(i,a,b) for(ll i=a;i<b;i++)
#define repr(i,n) for(ll i=n-1;i>=0;i--)
#define all(x) x.begin(),x.end()
#define pq priority_queue<ll>
#define pqg priority_queue<ll,vector<ll>,greater<ll>>
#define LB(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define UB(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
#define ERASE(v) sort(v.begin(),v.end());v.erase(unique(v.begin(),v.end()),v.end())
// #define int ll
using namespace std;
const ll INF = (1 << 30 ) - 1;
const ll LLINF = (1LL << 60LL);
const ll MOD = 1000000007;
const ll mod = 998244353;
const ll MAX = 1100000;
const double pi = acos(-1);
const double eps = 1e-10;
ll dx[4] ={1,0,-1,0} , dy[4] ={0,1,0,-1};
 
 
struct Timer{
    chrono::system_clock::time_point start, end;
    Timer(){ start = chrono::system_clock::now(); }
    ~Timer(){
        end = chrono::system_clock::now();
        auto msec = chrono::duration_cast<chrono::milliseconds>(end - start).count();
        cerr<<"time : "<<msec<<" ms"<<endl;
    }
};
 
 



signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    Timer TM;
    

    ll n;
    ll ans=0;
    string s;
    unordered_map<pair<string,string>,ll> mp;
    // map<pair<string,string>,ll> mp;
    cin>>n>>s;
    rep(bit,(1<<n)){
        string u="",t="";
        rep(i,n){
            if(bit&(1<<i)){
                u+=s[i];
            }
            else t+=s[i];
        }
        ++mp[make_pair(u,t)];
        // cout<<u+'0'+t<<endl;
    }
    rep(bit,(1<<n)){
        string u="",t="";
        rep(i,n){
            if(bit&(1<<i)){
                u=s[i+n]+u;
            }
            else t=s[i+n]+t;
        }
        ans+=mp[make_pair(t,u)];
    }
    cout<<ans<<endl;

    
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:62:43: error: use of deleted function 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map() [with _Key = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; _Tp = long long int; _Hash = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _Pred = std::equal_to<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _Alloc = std::allocator<std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int> >]'
   62 |     unordered_map<pair<string,string>,ll> mp;
      |                                           ^~
In file included from /usr/include/c++/14/unordered_map:41,
                 from /usr/include/c++/14/functional:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53,
                 from a.cc:3:
/usr/include/c++/14/bits/unordered_map.h:148:7: note: 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map() [with _Key = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; _Tp = long long int; _Hash = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _Pred = std::equal_to<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _Alloc = std::allocator<std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int> >]' is implicitly deleted because the default definition would be ill-formed:
  148 |       unordered_map() = default;
      |       ^~~~~~~~~~~~~
/usr/include/c++/14/bits/unordered_map.h: At global scope:
/usr/include/c++/14/bits/unordered_map.h:148:7: error: use of deleted function 'std::_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::_Hashtable() [with _Key = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; _Value = std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int>; _Alloc = std::allocator<std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int> >; _ExtractKey = std::__detail::_Select1st; _Equal = std::equal_to<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _Hash = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; _RehashPolicy = std::__detail::_Prime_rehash_policy; _Traits = std::__detail::_Hashtable_traits<true, false, true>]'
In file included from /usr/include/c++/14/bits/unordered_map.h:33:
/usr/include/c++/14/bits/hashtable.h:539:7: note: 'std::_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::_Hashtable() [with _Key = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; _Value = std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int>; _Alloc = std::allocator<std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int> >; _ExtractKey = std::__detail::_Select1st; _Equal = std::equal_to<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _Hash = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; _RehashPolicy = std::__detail::_Prime_rehash_policy; _Traits = std::__detail::_Hashtable_traits<true, false, true>]' is implicitly deleted because the default definition would be ill-formed:
  539 |       _Hashtable() = default;
      |       ^~~~~~~~~~
/usr/include/c++/14/bits/hashtable.h:539:7: error: use of deleted function 'std::__detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal, _Hash, _RangeHash, _Unused, _Traits>::_Hashtable_base() [with _Key = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; _Value = std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int>; _ExtractKey = std::__detail::_Select1st; _Equal = std::equal_to<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _Hash = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; _Traits = std::__detail::_Hashtable_traits<true, false, true>]'
In file included from /usr/include/c++/14/bits/hashtable.h:35:
/usr/include/c++/14/bits/hashtable_policy.h:1731:7: note: 'std::__detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal, _Hash, _RangeHash, _Unused, _Traits>::_Hashtable_base() [with _Key = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; _Value = std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int>; _ExtractKey = std::__detail::_Select1st; _Equal = std::equal_to<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _Hash = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; _Traits = std::__detail::_Hashtable_traits<true, false, true>]' is implicitly deleted because the default definition would be ill-formed:
 1731 |       _Hashtable_base() = default;
      |       ^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1731:7: error: use of deleted function 'std::__detail::_Hash_code_base<_Key, _Value, _ExtractKey, _Hash, _RangeHash, _Unused, __cache_hash_code>::_Hash_code_base() [with _Key = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; _Value = std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int>; _ExtractKey = std::__detail::_Select1st; _Hash = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; bool __cache_hash_code = true]'
/usr/include/c++/14/bits/hashtable_policy.h: In instantiation of 'std::__detail::_Hashtable_ebo_helper<_Nm, _Tp, true>::_Hashtable_ebo_helper() [with int _Nm = 1; _Tp = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >]':
/usr/include/c++/14/bits/hashtable_policy.h:1328:7:   required from here
 1328 |       _Hash_code_base() = default;
      |       ^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1245:49: error: use of deleted function 'std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >::hash()'
 1245 |       _Hashtable_ebo_helper() noexcept(noexcept(_Tp())) : _Tp() { }
      |                                                 ^~~~~
In file included from /usr/include/c++/14/string_view:50,
                 from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/functional_hash.h:102:12: note: 'std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >::hash()' is implicitly deleted because the default definition would be ill-formed:
  102 |     struct hash : __hash_enum<_Tp>
      |            ^~~~
/usr/include/c++/14/bits/functional_hash.h:102:12: error: no matching function for call to 'std::__hash_enum<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, false>::__hash_enum()'
/usr/include/c++/14/bits/functional_hash.h:83:7: note: candidate: 'std::__hash_enum<_Tp, <anonymous> >::__hash_enum(std::__hash_enum<_Tp, <anonymous> >&&) [with _Tp = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; bool <anonymous> = false]'
   83 |       __hash_enum(__hash_enum&&);
      |       ^~~~~~~~~~~
/usr/include/c++/14/bits/functional_hash.h:83:7: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/functional_hash.h:102:12: error: 'std::__hash_enum<_Tp, <anonymous> >::~__hash_enum() [with _Tp = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; bool <anonymous> = false]' is private within this context
  102 |     struct hash : __hash_enum<_Tp>
      |            ^~~~
/usr/include/c++/14/bits/functional_hash.h:84:7: note: declared private here
   84 |       ~__hash_enum();
      |       ^
/usr/include/c++/14/bits/hashtable_policy.h:1245:49: note: use '-fdiagnostics-all-candidates' to display considered candidates
 1245 |       _Hashtable_ebo_helper() noexcept(noexcept(_Tp())) : _Tp() { }
      |                                                 ^~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1328:7: note: 'std::__detail::_Hash_code_base<_Key, _Value, _ExtractKey, _Hash, _RangeHash, _Unused, __cache_hash_code>::_Hash_code_base() [with _Key = std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >; _Value = std::pair<const std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> >, long long int>; _ExtractKey = std::__detail::_Select1st; _Hash = std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; bool __cache_hash_code = true]' is implicitly deleted because the default definition would be ill-formed:
 1328 |       _Hash_code_base() = default;
      |       ^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1328:7: error: use of deleted function 'std::__detail::_Hashtable_ebo_helper<1, std::hash<std::pair<std::__cxx11::basic_string<char>, std::__cxx11::basic_string<char> > >, true>::~_Hashtable_ebo_helper()'
/usr/include/c++/14/bits/hashtable_p