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

typedef int_fast32_t int32;
typedef int_fast64_t int64;

const int32 inf = 1e9+7;
const int32 MOD = 1000000007;
const int64 llinf = 1e18;

#define YES(n) cout << ((n) ? "YES\n" : "NO\n"  )
#define Yes(n) cout << ((n) ? "Yes\n" : "No\n"  )
#define POSSIBLE(n) cout << ((n) ? "POSSIBLE\n" : "IMPOSSIBLE\n"  )
#define ANS(n) cout << (n) << "\n"
#define REP(i,n) for(int64 i=0;i<(n);++i)
#define FOR(i,a,b) for(int64 i=(a);i<(b);i++)
#define FORR(i,a,b) for(int64 i=(a);i>=(b);i--)
#define all(obj) (obj).begin(),(obj).end()
#define rall(obj) (obj).rbegin(),(obj).rend()
#define fi first
#define se second
#define pb(a) push_back(a)
typedef pair<int32,int32> pii;
typedef pair<int64,int64> pll;

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

template<int64 mod>
struct ModInt{
  int64 x;
  constexpr ModInt(int64 y = 0):x((y%mod+mod)%mod){}
  constexpr ModInt& operator+=(const ModInt& a){
    if((x += a.x) >= mod) x -= mod;
    return *this;
  }
  constexpr ModInt& operator-=(const ModInt& a){
    if((x -= a.x) < 0)x += mod;
    return *this;
  }
  constexpr ModInt& operator*=(const ModInt& a){
    x = x * a.x % mod;
    return *this;
  }
  constexpr ModInt& operator/=(const ModInt& a){
    *this *= a.inv();
    return *this;
  }
  constexpr ModInt operator-() const {
    return ModInt(-x);
  }
  constexpr ModInt operator+(const ModInt& a) const {
    return ModInt(*this) += a;
  }
  constexpr ModInt operator-(const ModInt& a) const {
    return ModInt(*this) -= a;
  }
  constexpr ModInt operator*(const ModInt& a) const {
    return ModInt(*this) *= a;
  }
  constexpr ModInt operator/(const ModInt& a) const {
    return ModInt(*this) /= a;
  }
  constexpr ModInt operator++(){
    *this += ModInt(1);
    return *this;
  }
  constexpr ModInt operator++(int){
    ModInt old = *this;
    ++*this;
    return old;
  }
  constexpr ModInt operator--(){
    *this -= ModInt(1);
    return *this;
  }
  constexpr ModInt operator--(int){
    ModInt old = *this;
    --*this;
    return old;
  }
  constexpr bool operator==(const ModInt& a) const {
    return x == a.x;
  }
  constexpr bool operator!=(const ModInt& a) const {
    return x != a.x;
  }
  constexpr ModInt pow(int64 r) const {
    if(!r)return 1;
    ModInt res = pow(r>>1);
    res *= res;
    if(r & 1) res *= *this;
    return res;
  }
  constexpr ModInt inv() const {
    return pow(mod-2);
  }
  friend istream& operator>>(istream& is, ModInt& a){
    int64 t;
    is >> t;
    a = ModInt(t);
    return is;
  }
  friend ostream& operator<<(ostream& os, const ModInt& a){
    return os << a.x;
  }
};
using mint = ModInt<MOD>;

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  int32 k;
  string s;
  cin >> k >> s;
  int32 n = s.size();
  // vector<vector<mint>> dp(n+k+1,vector<mint>(n+1,0));
  // dp[0][0] = 1;
  // REP(i,n+k)REP(j,n+1){
  //   if(j < n){
  //     dp[i+1][j] += dp[i][j] * 25;
  //     dp[i+1][j+1] += dp[i][j];
  //   }else{
  //     // dp[i+1][j] += dp[i][j] * 26;
  //   }
  // }
  // REP(i,n+k+1){
  //   REP(j,n+1){
  //     cout << dp[i][j] << " ";
  //   }
  //   cout << endl;
  // }

  vector<mint> fact(n+k+1,1);
  REP(i,n+k)fact[i+1] = fact[i] * (i+1);
  vector<mint> ifact(n+k+1);
  ifact[n+k] = fact[n+k].inv();
  FORR(i,n+k,1)ifact[i-1] = ifact[i] * i;
  auto comb = [&](int32 n, int32 r){return fact[n] * ifact[n-r] * ifact[r];};

  vector<mint> a(k+1);
  mint sum = 0;
  REP(i,k+1){
    sum += i+1;
    a[i] = mint(25).pow(i) * comb(n+i-1 , n-1);
    // cout << a[i] << " ";
  }

  mint ans = 0;
  REP(i,k+1){
    ans += a[i] * mint(26).pow(k-i);
  }
  ANS(ans);
   return 0;
}

Measured memory_bytes: 43328