#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using P = pair<int, int>;
using PLL = pair<ll, ll>;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define repn(i,n) for(int i = 0; i <= (int)(n); i++)
#define srep(i,l,n) for(int i = l; i < (int)(n); i++)
#define srepn(i,l,n) for(int i = l; i <= (int)(n); i++)
#define drep(i,n) for(int i = (int)(n-1); i >= 0; i--)
#define drepn(i,n) for(int i = (int)(n); i >= 0; i--)
#define size(s) (int)s.size()
#define debug(var)  do{std::cout << #var << " : ";view(var);}while(0)
template<typename T> void view(T e){std::cout << e << std::endl;}
template<typename T> void view(const std::vector<T>& v){for(const auto& e : v){ std::cout << e << " "; } std::cout << std::endl;}
template<typename T> void view(const std::vector<std::vector<T> >& vv){ for(const auto& v : vv){ view(v); } }
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<class T = int> using V = vector<T>;
template<class T = int> using VV = vector<V<T>>;
bool isIn(int i, int j, int h, int w) {return i >= 0 && i < h && j >= 0 && j < w;}
void Yes(){cout << "Yes" << endl;}
void No(){cout << "No" << endl;}
void YES(){cout << "YES" << endl;}
void NO(){cout << "NO" << endl;}
void err() {cout << -1 << endl;}
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define pb push_back
#define ep emplace_back

const int MOD = 1000000007;
const int INF = 1e9;

#define PI acos(-1);
int dx[4] = {1,-1,0,0};
int dy[4] = {0,0,1,-1};
int ddx[8] = {1,1,1,-1,-1,-1,0,0};
int ddy[8] = {0,1,-1,0,1,-1,1,-1};

const ll MAX = 2000000;
ll inv[MAX], fac[MAX], finv[MAX];

void settable() {
   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;
   }
}
ll choose(ll n, ll k){
   if (n < k) return 0;
   if (n < 0 || k < 0) return 0;
   return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

ll modpow(ll n, ll k){
   ll rtn = 1;
   while(k > 0){
       if(k&1) rtn = rtn * n % MOD;
       n = n * n % MOD;
       k = k >> 1;
   }
   return rtn;
}

const int mod = 1000000007;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x=0):x((x%mod+mod)%mod){}
  mint operator-() const { return mint(-x);}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod-a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res+=a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res-=a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res*=a;
  }
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }
 
  // for prime mod
  mint inv() const {
    return pow(mod-2);
  }
  mint& operator/=(const mint a) {
    return (*this) *= a.inv();
  }
  mint operator/(const mint a) const {
    mint res(*this);
    return res/=a;
  }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    settable();
    int k;
    string s;
    cin >> k >> s;
    mint ans = 0;
    srepn(i, size(s), size(s) + k) {
      mint now = 1;
      now *= modpow(26, size(s)+k-i);
      now *= modpow(25, i-size(s));
      now *= choose(i-1, size(s)-1);
      ans += now;
    }
    cout << ans.x << endl;
}

Measured memory_bytes: 51108