#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <cmath>
#include <numeric>
#include <iomanip>
#include <stack>
#include <complex>
#include <functional>
#include <tuple>

using namespace std;

#define Rep(i,a,b) for(ll i = a; i < b; ++i)
#define rep(i,b) Rep(i,0,b)
#define allof(a) (a).begin(), (a).end()

#define Yes(q) ((q) ? "Yes" : "No")
#define YES(q) ((q) ? "YES" : "NO")
#define Possible(q) ((q) ? "Possible" : "Impossible")
#define POSSIBLE(q) ((q) ? "POSSIBLE" : "IMPOSSIBLE")

using ll = long long;

constexpr int inf = 1e9 + 7;
constexpr ll infll = 1ll << 60ll;
constexpr ll mod = 1e9 + 7;
// 0~3までは右下左上 4~7までは斜め
constexpr int dx[] = { 1, 0, -1, 0, 1, -1 };
constexpr int dy[] = { 0, 1, 0, -1, 1, 1 };

namespace {
    template<typename T> bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
    template<typename T> bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

    void Cout(long long x, const char* end = "\n") { std::cout << x << end; }
    template <typename T> void Cout(const T& x, const char* end = "\n") { std::cout << x << end; }
    template <typename T> void Cout(const std::vector<T>& x, const char* sep = " ", const char* end = "\n") { for (std::size_t i = 0, sz = x.size(); i < sz; ++i) { std::cout << x[i] << (i == sz - 1 ? end : sep); } }

    // 標準入出力
    struct inp {
        std::size_t szi, szj;
        inp(std::size_t _szi = 1, std::size_t _szj = 1) : szi(_szi), szj(_szj) {}
        template <typename T> operator T () const { T a; std::cin >> a; return a; }
        template <typename T> operator std::vector<T>() const { std::vector<T> a(szi); for (std::size_t i = 0; i < szi; ++i) std::cin >> a[i]; return a; }
        template <typename T> operator std::vector<std::vector<T>>() const {
            std::vector<std::vector<T>> a(szi, std::vector<T>(szj));
            for (std::size_t i = 0; i < szi; ++i) for (std::size_t j = 0; j < szj; ++j) cin >> a[i][j]; return a;
        }
    };
    inp inp1;

    ll modpow(ll a, ll n) {
        ll result = 1;
        ll base = a;
        ll mask = 1;
        while (mask <= n) {
            if (n & mask) (result *= base) %= mod;
            mask <<= 1;
            (base *= base) %= mod;
        }
        return result;
    }

    ll pow(ll a, ll n) {
        ll result = 1;
        ll base = a;
        ll mask = 1;
        while (mask <= n) {
            if (n & mask) result *= base;
            mask <<= 1;
            base *= base;
        }
        return result;
    }

    template<int MOD> struct Fp {
        long long val;
        constexpr Fp(long long v = 0) noexcept : val(v% MOD) {
            if (val < 0) val += MOD;
        }
        constexpr int getmod() { return MOD; }
        constexpr Fp operator - () const noexcept {
            return val ? MOD - val : 0;
        }
        constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
        constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
        constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
        constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
        constexpr Fp& operator += (const Fp& r) noexcept {
            val += r.val;
            if (val >= MOD) val -= MOD;
            return *this;
        }
        constexpr Fp& operator -= (const Fp& r) noexcept {
            val -= r.val;
            if (val < 0) val += MOD;
            return *this;
        }
        constexpr Fp& operator *= (const Fp& r) noexcept {
            val = val * r.val % MOD;
            return *this;
        }
        constexpr Fp& operator /= (const Fp& r) noexcept {
            long long a = r.val, b = MOD, u = 1, v = 0;
            while (b) {
                long long t = a / b;
                a -= t * b; std::swap(a, b);
                u -= t * v; std::swap(u, v);
            }
            val = val * u % MOD;
            if (val < 0) val += MOD;
            return *this;
        }
        constexpr bool operator == (const Fp& r) const noexcept {
            return this->val == r.val;
        }
        constexpr bool operator != (const Fp& r) const noexcept {
            return this->val != r.val;
        }
        friend constexpr std::ostream& operator << (std::ostream& os, const Fp<MOD>& x) noexcept {
            return os << x.val;
        }
        constexpr Fp pow(long long n) noexcept {
            if (n == 0) return 1;
            auto t = pow(val, n / 2);
            t = t * t;
            if (n & 1) t = t * val;
            return t;
        }
    };
    using mint = Fp<mod>;

    // けんちょんさんのを自分なりに改造 tada
// Combination を高速にテーブル化させるライブラリ
// MOD >= 1 の場合は，MODで割った余りを返す 構築 O(n) 取得 O(1)
// MOD <= 0 の場合は，余りを考慮しない 構築 O(n^2) 取得 O(1) オーバーフローに注意
    template<int MOD> class COM {
    public:
        COM(long long max_n = 2e6) noexcept : kMax_(max_n * 4LL + 1LL) {
            if (MOD >= 1) Init();
            else InitNoMod();
        };

        //　二項係数計算
        long long Com(int n, int k) {
            if (n < k) return 0LL;
            if (n < 0 || k < 0) return 0LL;
            if (MOD >= 1) return fac_[n] * (finv_[k] * finv_[n - k] % MOD) % MOD;
            else return com_table_[n * kMax_ + k];
        }

        // 重複組み合わせ
        long long H(int n, int k) {
            return Com(n + k - 1, k);
        }


    private:
        void Init() {
            fac_.resize(kMax_);
            finv_.resize(kMax_);
            inv_.resize(kMax_);

            fac_[0] = fac_[1] = 1;
            finv_[0] = finv_[1] = 1;
            inv_[1] = 1;

            for (int i = 2; i < kMax_; ++i) {
                fac_[i] = fac_[i - 1] * i % MOD;
                inv_[i] = MOD - inv_[MOD % i] * (MOD / i) % MOD;
                finv_[i] = finv_[i - 1] * inv_[i] % MOD;
            }
        }
        void InitNoMod() {
            com_table_ = std::vector<long long>(kMax_ * kMax_, 0LL);

            for (int i = 0; i < kMax_; ++i) {
                for (int j = 0; j <= i; ++j) {
                    if (j == 0 || j == i) com_table_[i * kMax_ + j] = 1LL;
                    else {
                        com_table_[i * kMax_ + j] =  // パスカルの三角形を利用している
                            (com_table_[(i - 1) * kMax_ + j - 1] + com_table_[(i - 1) * kMax_ + j]);
                    }
                }
            }

            //rep(i, kMax_) {
            //    rep(j, i + 1) {
            //        cout << com_table_[i * kMax_ + j] << " ";
            //    }
            //    cout << endl;
            //}
        }

        std::vector<long long> fac_, finv_, inv_;
        std::vector<long long> com_table_;
        const long long kMax_;
    };
}

int main() {

    int k = inp1;
    string s = inp1;
    ll n = s.length();
    ll sz = k + n;

    COM<mod> com;
    //mint ans = com.Com(k + n + 1, k);

    mint ans = 0;
    // 右端にi個ある
    rep(i, k + 1) {
        mint add = 1;
        add *= modpow(25, k - i);
        add *= com.Com(k - i + n - 1, k - i);
        add *= modpow(26, i);
        ans += add;
    }

    Cout(ans);

    return 0;
}


Measured memory_bytes: 191900