#include <bits/stdc++.h>

using namespace std;

const int OO = 1e9;
const double EPS = 1e-9;

#define ndl cout << '\n'
#define sz(v) int(v.size())
#define pb push_back
#define mp make_pair
#define fs first
#define sc second
#define present(a, x) (a.find(x) != a.end())
#ifdef LOCAL
#define db(...) ({cout << "> Line " << __LINE__  \
		<< ": "; _db(#__VA_ARGS__, __VA_ARGS__);})
#define RNG() rng()
#else
#define db(...) true
#define RNG() true
#endif

template<class T>
void _db(const char *dbStr, T e) {
	cout << dbStr << " = " << e << endl;
}
template<class T, class... L>
void _db(const char *dbStr, T e, L... r) {
  while(*dbStr != ',') cout << *dbStr++;
  cout << " = " << e << ','; _db(dbStr + 1, r...);
}
template<class S, class T>
ostream& operator<<(ostream& o, const map<S, T>& v) {
	o << "["; int i = 0;
	for (const pair<S, T>& pr : v) o << (!i++ ? "" : ", ") << "{"
	<< pr.fs << " : " << pr.sc << "}"; return o << "]";
}
template<template <class, class...> class S, class T, class... L>
ostream& operator<<(ostream& o, const S<T, L...>& v) {
	o << "["; int i = 0;
	for (const auto& e : v) o << (!i++ ? "" : ", ") << e;
	return o << "]";
}
template<class S, class T>
ostream& operator<<(ostream& o, const pair<S, T>& pr) {
	return o << "(" << pr.fs << ", " << pr.sc << ")";
}
ostream& operator<<(ostream& o, const string& s) {
	for (const char& c : s) o << c;
	return o;
}

template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = VV<V<T>>;
using ll = long long;
using pii = pair<int, int>;
using vi = V<int>;
using vii = V<pii>;
using vvi = VV<int>;
using mii = map<int, int>;
using umii = unordered_map<int, int>;
using si = set<int>;
using usi = unordered_set<int>;


const int MOD = 1000000007;

ll power(ll num, ll exp) {
	ll ret = 1;
	while (exp) {
		if (exp & 1)
			ret = (ret * num) % MOD;
		num = (num * num) % MOD;
		exp >>= 1;
	}
	return ret;
}
ll inv(ll a, ll b) {
	return 1 < a ? b - inv(b % a, a) * b / a : 1;
}

const int MX = 2e6 + 5;
int fact[MX], factInv[MX], N, K;
string S;

//int dp(int idx1, int idx2) {
//	db(idx1, idx2);
//	if (idx2 == N)
//		return power(26, N + K - idx1);
//	if (idx1 == N + K)
//		return 0;
//	int& ret = mem[idx1][idx2];
//	if (ret != -1)
//		return ret;
//	return ret = (25LL * dp(idx1 + 1, idx2) + dp(idx1 + 1, idx2 + 1)) % MOD;
//}

int ch(int n, int k) {
	int ret = (fact[n] * 1LL * factInv[k]) % MOD;
	ret = (ret * 1LL * factInv[n - k]) % MOD;
	return ret;
}


int main() {
	#ifdef LOCAL
	auto stTime = clock();
//	freopen("in.txt", "r", stdin);
	mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
	#endif
	ios::sync_with_stdio(false);
	cout.precision(10);
	cin.tie(0);

//	memset(mem, -1, sizeof(mem));

	fact[0] = factInv[0] = 1;

	for (int i = 1; i < MX; ++i) {
		fact[i] = (fact[i - 1] * 1LL * i) % MOD;
		factInv[i] = inv(fact[i], MOD);
	}

	cin >> K >> S;

	N = sz(S);

	ll ans = 0;

	for (int i = N; i <= N + K; ++i) {
		ll add = ch(i - 1, N - 1) * power(25, i - N);
		add %= MOD;
		add *= power(26, N + K - i);
		add %= MOD;
		ans = (ans + add) % MOD;
	}

	cout << ans << '\n';



	#ifdef LOCAL
	cout << "\n\n\nExecution time: " <<
		(clock() - stTime) * 1e3 / CLOCKS_PER_SEC << " ms" << endl;
	#endif
	return 0;
}


Measured memory_bytes: 19868