#include <bits/stdc++.h>
using namespace std;

// template {{{
#define  range(i, l, r) for (int i = (int)(l); i < (int)(r); (i) += 1)
#define rrange(i, l, r) for (int i = (int)(r) - 1; i >= (int)(l); (i) -= 1)

#define  whole(f, x, ...) ([&](decltype((x)) container) { return (f)(  begin(container),  end(container), ## __VA_ARGS__); })(x)
#define rwhole(f, x, ...) ([&](decltype((x)) container) { return (f)( rbegin(container), rend(container), ## __VA_ARGS__); })(x)

#define debug(x) cerr << "(" << __LINE__ << ")" << #x << ": " << (x) << endl

using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;

// constexpr i32 mod   = 998244353;
constexpr i32 mod   = 1e9 + 7;
constexpr i32 inf   = 1001001001;
constexpr i64 infll = 1001001001001001001ll;

constexpr int dx[] = {0, -1, 1, 0, -1, 1, -1, 1};
constexpr int dy[] = {-1, 0, 0, 1, -1, -1, 1, 1};

struct IoSetup { IoSetup(int x = 15){ cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(x); cerr << fixed << setprecision(x); } } iosetup;

template <typename T = i64> T input() { T x; cin >> x; return x; }

template <typename T> ostream &operator<<(ostream &os, vector<T> &v) { range(i, 0, v.size()) { os << v[i] << (i + 1 != v.size() ? " " : ""); } return os; }
template <typename T> istream &operator>>(istream &is, vector<T> &v) { for (T &in : v) is >> in; return is; }

template <typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
template <typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }

template <typename T> vector<T> make_vector(size_t a, T b) { return vector<T>(a, b); }
template <typename... Ts> auto make_vector(size_t a, Ts... ts) { return vector<decltype(make_vector(ts...))>(a, make_vector(ts...)); }

template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
// }}}

// mod_int {{{
template < int mod >
class mod_int {
    using i32 = int_fast32_t;
    using i64 = int_fast64_t;

    i32 num_;

    public:
    mod_int() : num_(0) {}
    mod_int(i64 num_) : num_(num_ >= 0 ? num_ % mod : (mod + num_ % mod) % mod) {}

    inline i32 num() const { return num_; }
    operator i64() { return num_; }

    inline mod_int inverse() const {
        i32 a = num_, b = mod, u = 1, v = 0, t;
        while (b) { t = a / b; std::swap(a -= t * b, b); std::swap(u -= t * v, v); }
        return mod_int(u);
    }

    mod_int operator~() const { return inverse(); }
    mod_int operator+() const { return *this; }
    mod_int operator-() const { return mod_int(-num_); }

    mod_int &operator+=(const mod_int &rhs) { if ((num_ += rhs.num_) >= mod) num_ -= mod; return *this; }
    mod_int &operator-=(const mod_int &rhs) { if ((num_ -= rhs.num_) <  0)   num_ += mod; return *this; }
    mod_int &operator*=(const mod_int &rhs) { num_ = i64(num_) * rhs.num_ % mod; return *this; }
    mod_int &operator/=(const mod_int &rhs) { return *this *= rhs.inverse(); }

    mod_int operator+(const mod_int &rhs) const { return mod_int(*this) += rhs; }
    mod_int operator-(const mod_int &rhs) const { return mod_int(*this) -= rhs; }
    mod_int operator*(const mod_int &rhs) const { return mod_int(*this) *= rhs; }
    mod_int operator/(const mod_int &rhs) const { return mod_int(*this) /= rhs; }

    bool operator==(const mod_int &rhs) const { return num_ == rhs.num_; }
    bool operator!=(const mod_int &rhs) const { return num_ != rhs.num_; }

    friend std::ostream &operator<<(std::ostream &os, const mod_int &rhs) {
        return os << rhs.num_;
    }

    friend std::istream &operator>>(std::istream &is, mod_int &rhs) {
        i64 num; is >> num; rhs = mod_int< mod >(num);
        return is;
    }

    friend mod_int pow(mod_int lhs, i64 rhs) {
        mod_int res(1);
        for (; rhs; rhs >>= 1) {
            if (rhs & 1) res *= lhs;
            lhs *= lhs;
        }
        return res;
    }
};
// }}}

using modint = mod_int< mod >;

// mod combination {{{
template< typename T >
class mod_combinatorics {

    std::size_t size_;
    std::vector< T > fact_, finv_, invs_;

    public:
    mod_combinatorics(std::size_t size) : size_(size + 1), fact_(size_), finv_(size_), invs_(size_) {
        fact_[0] = 1;
        for (int i = 1; i < size_; ++i) fact_[i] = fact_[i - 1] * T(i);

        finv_.back() = fact_.back().inverse();
        for (int i = int_fast32_t(size_) - 2; i >= 0; --i) finv_[i] = finv_[i + 1] * T(i + 1);
        for (int i = 0; i < size; ++i) invs_[i] = finv_[i] * fact_[i - 1];
    }

    inline void boundary_check(int n) const {
        if (size_ < n) {
            std::cerr << "boudary error" << std::endl;
        }
    }

    // k!
    T fact(int k) const {
        boundary_check(k);
        return fact_[k];
    }

    // P(n, k)
    T permutation(int n, int k) const {
        boundary_check(n);
        if (k < 0 || n < k) return T(0);
        return fact_[n] * finv_[n - k];
    }

    // C(n, k)
    T combination(int n, int k) const {
        boundary_check(n);
        if (k < 0 || n < k) return T(0);
        return fact_[n] * finv_[k] * finv_[n - k];
    }

    // H(n, k)
    T multichoose(int n, int k) const {
        boundary_check(n + k - 1);
        if (n < 0 || k < 0) return T(0);
        return fact_[n + k - 1] * finv_[k] * finv_[n - 1];
    }
};
// }}}

void solver() {
    int k = input();
    string s;
    cin >> s;

    mod_combinatorics< modint > mc(3000000);

    modint ans = 0;
    range(i, s.size(), s.size() + k + 1) {
        ans += mc.combination(i - 1, s.size() - 1) * pow(modint(25), i - s.size()) * pow(modint(26), s.size() + k - i);
    }

    cout << ans << endl;
}

signed main(int argc, char *argv[]) {
    solver();
}


Measured memory_bytes: 74676