#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
 
#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;
 
typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;
 
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
 
#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define trav(a,x) for (auto& a : x)
 
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define ins insert

template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
 
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
 
const int MOD = 1000000007;
const char nl = '\n';
const int MX = 2000001; //check the limits, dummy
struct mi {
    ll v; explicit operator ll() const { return v; }
    mi() { v = 0; }
    mi(ll _v) {
        v = (-MOD < _v && _v < MOD) ? _v : _v % MOD;
        if (v < 0) v += MOD;
    }
    friend bool operator==(const mi& a, const mi& b) {
        return a.v == b.v; }
    friend bool operator!=(const mi& a, const mi& b) {
        return !(a == b); }
    friend bool operator<(const mi& a, const mi& b) {
        return a.v < b.v; }

    mi& operator+=(const mi& m) {
        if ((v += m.v) >= MOD) v -= MOD;
        return *this; }
    mi& operator-=(const mi& m) {
        if ((v -= m.v) < 0) v += MOD;
        return *this; }
    mi& operator*=(const mi& m) {
        v = v*m.v%MOD; return *this; }
    mi& operator/=(const mi& m) { return (*this) *= inv(m); }
    friend mi pow(mi a, ll p) {
        mi ans = 1; assert(p >= 0);
        for (; p; p /= 2, a *= a) if (p&1) ans *= a;
        return ans;
    }
    friend mi inv(const mi& a) { assert(a.v != 0);
        return pow(a,MOD-2); }

    mi operator-() const { return mi(-v); }
    mi& operator++() { return *this += 1; }
    mi& operator--() { return *this -= 1; }
    mi operator++(int) { mi temp; temp.v = v++; return temp; }
    mi operator--(int) { mi temp; temp.v = v--; return temp; }
    friend mi operator+(mi a, const mi& b) { return a += b; }
    friend mi operator-(mi a, const mi& b) { return a -= b; }
    friend mi operator*(mi a, const mi& b) { return a *= b; }
    friend mi operator/(mi a, const mi& b) { return a /= b; }
    friend ostream& operator<<(ostream& os, const mi& m) {
        os << m.v; return os;
    }
    friend istream& operator>>(istream& is, mi& m) {
        ll x; is >> x;
        m.v = x;
        return is;
    }
};


typedef vector<mi> vmi;
typedef pair<mi,mi> pmi;
typedef vector<pmi> vpmi;
mi facs[MX];
mi facInvs[MX];

mi choose(mi _a, mi _b) {
    ll a = (ll) _a, b = (ll) _b;
    if (b > a) return 0;
    if (a < 0) return 0;
    if (b < 0) return 0;
    mi cur = facs[a];
    cur = cur * facInvs[b];
    cur = cur * facInvs[a-b];
    return cur;
}

void initFacs() {
    facs[0] = 1;
    facInvs[0] = 1;
    FOR(i, 1, MX) {
        facs[i] = (facs[i-1] * i);
        facInvs[i] = inv(facs[i]);
    }
}

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);    
	
    int K; cin >> K;
    string S; cin >> S;
    int N; N = sz(S);
    initFacs();

    mi ans = 0;
    F0R(i, K+1) {
        ans += pow(mi(26), K-i) * pow((mi) 25, i) * choose(i+N-1, N-1);
    }

    cout << ans << nl;
	
	return 0;
}
 
// read the question correctly (ll vs int)
// template by bqi343


Measured memory_bytes: 35548