#include <bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define ll long long
#define ull unsigned long long
#define ld long double
#define vl vector<long long>
#define vvl vector<vector<long long>>
#define rbf(a, x) for (auto& a : x)
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define rep2(i, s, n) for (ll i = (s); i < (ll)(n); i++)
#define drep(i, x) for (ll i = ((ll)(x)-1); i >= 0; i--)
#define pll pair<long long,long long>
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define vvc vector<vector<char>>
#define vc vector<char>
#define vvb vector<vector<bool>>
#define vb vector<bool>
#define Maxe(x) *max_element(all(x))
#define Mine(x) *min_element(all(x))
#define Size(x) ((ll)(x).size())
#define umap unordered_map
const long long INF = 1LL << 60;
const long double pi = 3.1415926535897932;
#define Fi first
#define Se second
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};

    template<typename Num>
        constexpr Num mypow(Num a, long long b) {
            if(b==0)return 1;
            if (a==0)return 0;
            Num x = 1;
              while (b > 0) {
                if(b & 1)x*=a;
                a*=a;
                b >>= 1;
              }
              return x;
        }

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

const ll MAX=3000005;
const ll MOD=1000000007;

long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; 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;
    }
}

// 二項係数計算
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

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; swap(a, b);
            u -= t * v; 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 ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
        return os << x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};

using mint = Fp<MOD>;

    signed main(){
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
        COMinit();
        ll k;
        string s;
        cin>>k>>s;
        ll n=Size(s);
        vector<mint> p25(k+1,1);
        vector<mint> p26(k+1,1);
        rep(i,k){
            p25[i+1]=p25[i]*25;
            p26[i+1]=p26[i]*26;
        }
        mint ans=0;
        rep(i,k+1){
            mint res=p25[i];
            res*=p26[k-i];
            res*=COM(i+n-1,n-1);
            ans+=res;
        }
        cout<<ans<<endl;
    }

Measured memory_bytes: 90384