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

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;

template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename U> using ordered_map = tree<T, U, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

typedef long long ll;
typedef long double ld;
typedef double db;
typedef string str;

typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<str> vstr;

#define FOR(i,j,k,in) for(int i=(j); i < (k);i+=in)
#define FORD(i,j,k,in) for(int i=(j); i >=(k);i-=in)
#define REP(i,b) FOR(i,0,b,1)
#define REPD(i,b) FORD(i,b,0,1)
#define pb push_back 
#define mp make_pair
#define ff first
#define ss second
#define all(x) begin(x), end(x)
#define rsz resize 

const double EPS = 1e-9;
const int MOD = 1e9+7; // 998244353;
const ll INFF = 1e18;
const int INF = 1e9;
const ld PI = acos((ld)-1);
const vi dy = {1, 0, -1, 0, -1, 1, 1, -1};
const vi dx = {0, 1, 0, -1, -1, 1, -1, 1};

#ifdef DEBUG
#define DBG if(1)
#else
#define DBG if(0)
#endif

#define dbg(x) cout << "(" << #x << " : " << x << ")" << endl;
// ostreams
template <class T, class U>
ostream& operator<<(ostream& out, const pair<T, U> &par) {out << "[" << par.first << ";" << par.second << "]"; return out;}
template <class T>
ostream& operator<<(ostream& out, const set<T> &cont) { out << "{"; for( const auto &x:cont) out << x << ", "; out << "}"; return out; }
template <class T, class U>
ostream& operator<<(ostream& out, const map<T, U> &cont) {out << "{"; for( const auto &x:cont) out << x << ", "; out << "}"; return out; }
template<class T>
ostream& operator<<(ostream& out, const vector<T> &v){ out << "[";  REP(i, v.size()) out << v[i] << ", ";  out << "]"; return out;}
// istreams
template<class T>
istream& operator>>(istream& in, vector<T> &v){ for(auto &x : v) in >> x; return in; }
template<class T, class U>
istream& operator>>(istream& in, pair<T, U> &p){ in >> p.ff >> p.ss; return in; }
//searches
template<typename T, typename U>
T bsl(T lo, T hi, U f){ hi++; T mid; while(lo < hi){ mid = (lo + hi)/2; f(mid) ? hi = mid : lo = mid+1; } return lo; }
template<typename U>
double bsld(double lo, double hi, U f, double p = 1e-9){ int r = 3 + (int)log2((hi - lo)/p); double mid; while(r--){ mid = (lo + hi)/2; f(mid) ? hi = mid : lo = mid; } return (lo + hi)/2; }
template<typename T, typename U>
T bsh(T lo, T hi, U f){ lo--; T mid; while(lo < hi){ mid = (lo + hi + 1)/2; f(mid) ? lo = mid : hi = mid-1; } return lo; }
template<typename U>
double bshd(double lo, double hi, U f, double p = 1e-9){ int r = 3+(int)log2((hi - lo)/p); double mid; while(r--){ mid = (lo + hi)/2; f(mid) ? lo = mid : hi = mid; } return (lo + hi)/2; }
// some more utility functions
template<typename T>
pair<T, int> get_min(vector<T> &v){ typename vector<T> :: iterator it = min_element(v.begin(), v.end()); return mp(*it, it - v.begin());}
template<typename T>
pair<T, int> get_max(vector<T> &v){ typename vector<T> :: iterator it = max_element(v.begin(), v.end()); return mp(*it, it - v.begin());}        
template<typename T> bool ckmin(T& a, const T& b){return b < a ? a = b , true : false;}
template<typename T> bool ckmax(T& a, const T& b){return b > a ? a = b, true : false;}

const int mod = (int)1e9+7;
struct Mint{
    int val;
    Mint(){ val = 0; }
    Mint(long long v){
        val = (-mod <= v && v < mod) ? v : v%mod;
        if(val < 0) val+= mod;
    }
    // operators
    Mint operator-(){return Mint(-val);}
    Mint& operator+=(const Mint& other){ val+=other.val; if(val> mod) val-=mod; return *this;}
    Mint& operator-=(const Mint& other){ val-=other.val; if(val < 0) val+=mod; return *this;}
    Mint& operator*=(const Mint& other){ val=((long long)val*other.val)%mod; return *this;}
    friend Mint binpow(Mint a, long long p){
        Mint res(1);
        while(p > 0){
            if(p&1) res*=a; a*=a; p>>=1;
        }
        return res;
    }
    friend Mint inv(Mint a){ return binpow(a, mod-2); }
    Mint& operator/=(const Mint &other){ return (*this)*=inv(other);}
    
    friend Mint operator+(Mint a, const Mint& b){ return a+=b; }
    friend Mint operator-(Mint a, const Mint& b){ return a-=b; }
    friend Mint operator*(Mint a, const Mint& b){ return a*=b; }
    friend Mint operator/(Mint a, const Mint& b){ return a/=b; }
    
    bool operator==(const Mint &other){return val == other.val;}
    bool operator!=(const Mint &other){return val != other.val;}
    bool operator<(const Mint &other){return val < other.val;}
    // io
    friend ostream& operator<<(ostream &out, Mint &a){ return out << a.val; }
};
struct AcAutomaton{
    str s; int k;
	void read_in(){
		cin >> k >> s; 
	}
	void solve(){
        int n = s.length();
        vector<Mint> fact;
        fact.pb(Mint(1));
        REP(i, s.length() + k + 10) fact.pb(fact[i] * Mint((i+1)));
        auto ncr = [&](int nn, int rr){
            return (fact[nn]/fact[rr])/fact[nn-rr];
        };
        Mint res(0);
        FOR(i, n, n+k+1, 1){
            res += binpow(Mint(25), i - n) * binpow(Mint(26), k - (i - n)) * ncr(i-1, n-1);  
        }
        cout << res << endl;
	}
};
    
int main(){
 	ios_base::sync_with_stdio(false);
 	cin.tie(NULL); cout.tie(NULL);
	int tcase = 1;
	while(tcase--){
		AcAutomaton solver;
		solver.read_in();
		solver.solve();
	}
    return 0;
}

Measured memory_bytes: 12924