#pragma GCC optimize ("O3")
#include "bits/stdc++.h"

using namespace std;
using ll = long long int;

#define debugos cout
#define debug(v) {printf("L%d %s > ",__LINE__,#v);debugos<<(v)<<endl;}
#define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:(v)){debugos<<e<<" ";}debugos<<endl;}
#define debuga(m,w) {printf("L%d %s > ",__LINE__,#m);for(int x=0;x<(w);x++){debugos<<(m)[x]<<" ";}debugos<<endl;}
#define debugaa(m,h,w) {printf("L%d %s >\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){debugos<<(m)[y][x]<<" ";}debugos<<endl;}}
#define ALL(v) (v).begin(),(v).end()
#define repeat(cnt,l) for(remove_reference<remove_const<decltype(l)>::type>::type cnt=0;(cnt)<(l);++(cnt))
#define rrepeat(cnt,l) for(auto cnt=(l)-1;0<=(cnt);--(cnt))
#define iterate(cnt,b,e) for(auto cnt=(b);(cnt)!=(e);++(cnt))
#define diterate(cnt,b,e) for(auto cnt=(b);(cnt)!=(e);--(cnt))
const ll MD = 1000000007ll; const long double PI = 3.1415926535897932384626433832795L;
inline void assert_call(bool assertion, function<void()> f) { if (!assertion) { cerr << "assertion fault:" << endl; f(); abort(); } }
template<typename T1, typename T2> inline ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << '(' << p.first << ':' << p.second << ')'; return o; }
template<typename Vec> inline ostream& _ostream_vecprint(ostream& os, const Vec& a) {
    os << '['; for (const auto& e : a) os << ' ' << e << ' '; os << ']'; return os;
}
template<typename T> inline ostream& operator<<(ostream& o, const vector<T>& v) { return _ostream_vecprint(o, v); }
template<typename T, size_t S> inline ostream& operator<<(ostream& o, const array<T, S>& v) { return _ostream_vecprint(o, v); }
template<typename T> inline T& maxset(T& to, const T& val) { return to = max(to, val); }
template<typename T> inline T& minset(T& to, const T& val) { return to = min(to, val); }
void bye(string s, int code = 0) { cout << s << endl; exit(code); }
mt19937_64 randdev(8901016);
template<typename T> inline T rand(T l, T h) { return uniform_int_distribution<T>(l, h)(randdev); }
template<> inline double rand<double>(double l, double h) { return uniform_real_distribution<double>(l, h)(randdev); }
template<> inline float rand<float>(float l, float h) { return uniform_real_distribution<float>(l, h)(randdev); }

#if defined(_WIN32) || defined(_WIN64)
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#elif defined(__GNUC__)
#else
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
namespace {
#define isvisiblechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T> void input_integer(T& var) {
            var = 0; T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc && cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var * sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) { input_integer<int>(var); return *this; }
        inline MaiScanner& operator>>(long long& var) { input_integer<long long>(var); return *this; }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiblechar(cc); cc = getchar_unlocked());
            for (; isvisiblechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
            return *this;
        }
        template<typename IT> void in(IT begin, IT end) { for (auto it = begin; it != end; ++it) *this >> *it; }
    };
    class MaiPrinter {
    public:
        template<typename T>
        void output_integer(T var) {
            if (var == 0) { putchar_unlocked('0'); return; }
            if (var < 0)
                putchar_unlocked('-'),
                var = -var;
            char stack[32]; int stack_p = 0;
            while (var)
                stack[stack_p++] = '0' + (var % 10),
                var /= 10;
            while (stack_p)
                putchar_unlocked(stack[--stack_p]);
        }
        inline MaiPrinter& operator<<(char c) { putchar_unlocked(c); return *this; }
        inline MaiPrinter& operator<<(int var) { output_integer<int>(var); return *this; }
        inline MaiPrinter& operator<<(long long var) { output_integer<long long>(var); return *this; }
        inline MaiPrinter& operator<<(char* str_p) { while (*str_p) putchar_unlocked(*(str_p++)); return *this; }
        inline MaiPrinter& operator<<(const string& str) {
            const char* p = str.c_str();
            const char* l = p + str.size();
            while (p < l) putchar_unlocked(*p++);
            return *this;
        }
        template<typename IT> void join(IT begin, IT end, char sep = ' ') { for (bool b = 0; begin != end; ++begin, b = 1) b ? *this << sep << *begin : *this << *begin; }
    };
}
MaiScanner scanner;
MaiPrinter printer;

// bool guchokuu(ll a, ll b, ll c, ll d) {
//     repeat(t, 999) {
//         if (a > b) return false;
//         a -= b;
//         if (a <= c) a += d;
//     }
//     return true; // maybe
// }
// 
// bool guchoku(ll a, ll b, ll c, ll d) {
//     repeat(t, 999) {
//         a = a % b;
//         if (a > c) return false;
//         a += d;
//     }
//     return true; // maybe
// }
// 
// // YESなら0
// int solve(ll a, ll b, ll c, ll d) {
//     // day 1 false
//     if (a > b) return 1;
//     // day inf false
//     if (b > d) return 2;
//     // kirisute
//     if (b <= c) return 0;
// 
//     return 0;
// }
// 
// 
// 
// void test() {
//     repeat(_, 2000) {
//         ll a, b, c, d;
//         a = rand(1, 33);
//         b = rand(1, 33);
//         c = rand(1, 33);
//         d = rand(1, 33);
// 
//         bool ex = guchoku(a, b, c, d);
//         int ac = solve(a, b, c, d);
//         if (ex != (ac == 0)) {
//             cout << "fault" << endl;
//             cout << a << " " << b << " " << c << " " << d << endl;
//             cout << ac << endl;
//             exit(0);
//         }
//     }
//     cout << "ac" << endl;
// }


template<typename TKEY = char, typename TVAL = int>
struct TrieTree {
    TVAL value;
    map<TKEY, TrieTree> trie;
    TrieTree(TVAL v) :value(v) {}
    TrieTree() :value() {}

    template<typename IBEGIN, typename IEND>
    TVAL& operator()(IBEGIN begin, IEND end) {
        auto begin_succ = begin;
        return (begin == end) ? value
            : trie[*begin](++begin_succ, end);
    }
};

int N, N1, N2;

string str;

TrieTree<char, map<vector<char>, ll>> trie_red;

ll answer = 0;

void listing(int i, vector<char>& red, vector<char>& blue) {
    if (i < N1) {
        red.push_back(str[i]);
        listing(i + 1, red, blue);
        red.pop_back();
        blue.push_back(str[i]);
        listing(i + 1, red, blue);
        blue.pop_back();
    }
    else {

        trie_red(ALL(red))[blue] += 1; // ?
    }
}


void listing2(int i, vector<char>& red_, vector<char>& blue_) {
    if (i < N) {
        red_.push_back(str[i]);
        listing2(i + 1, red_, blue_);
        red_.pop_back();
        blue_.push_back(str[i]);
        listing2(i + 1, red_, blue_);
        blue_.pop_back();
    }
    else {
        vector<char> redr = red_; reverse(ALL(redr));
        answer += trie_red(blue_.rbegin(), blue_.rend())[redr];
    }
}


int main() {

    scanner >> N >> str;
    N *= 2;

    N1 = N / 2;
    N2 = N - N1;

    vector<char> redi, bluei;
    listing(0, redi, bluei);
    redi.clear(); bluei.clear();
    listing2(N1, redi, bluei);

    cout << answer << endl;


    return 0;
}

Measured memory_bytes: 114944