#define _CRT_SECURE_NO_WARNINGS
#define REL

#pragma GCC target ("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <deque>
#include <queue>
#include <iomanip>
#include <cstdio>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <string>
#include <set>
#include <bitset>
#include <cstdint>
#include <cstring>
#include <cassert>
#include <complex>
#include <stack> 
#include <random>

using namespace std;

typedef int64_t i64;
typedef long long LL;
typedef long long ll;
typedef long double LD;
typedef complex <LD> cld;
typedef unsigned int uint;
typedef complex <double> cd;
typedef unsigned long long ULL;

#define endl "\n"
#define dendl "\n\n"
#define mp make_pair
#define mt make_tuple
#define size(v) (int)v.size()
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()

/////////////////////////////////////////////////////////////////////

template <typename T>
T sqr(T a) {
	return a * a;
}

template <typename T>
int sign(T a) {
	if (a == 0)
		return 0;
	return (a > 0 ? 1 : -1);
}

template <typename T>
bool uax(T& a, const T b) {
	if (a < b) {
		a = b;
		return true;
	}
	return false;
}

template <typename T>
bool uin(T& a, const T b) {
	if (a > b) {
		a = b;
		return true;
	}
	return false;
}

template <typename T1, typename T2>
istream& operator >> (istream& in, pair<T1, T2>& p) {
	in >> p.first >> p.second;
	return in;
}

template <typename T1, typename T2>
ostream& operator << (ostream& out, pair<T1, T2>& p) {
	out << p.first << ' ' << p.second;
	return out;
}

mt19937_64 rnd(0);

const int LOG = 64;
const int N = (int)2e6 + 7;
const int MAXN = (int)1e6 + 7;
const int MOD = (int)1e9 + 7;
const int INF = (int)2e9 + 7;
const int CONST = 450;
const LL LINF = (i64)1e18;
const LD PI = 3.1415926535897932384626433832795;
const LD EPS = 1;

/////////////////////////////////////////////////////////////////////

int k;
string s;
int fact[N];

int add(int a, int b) {
	return (a + b) % MOD;
}

int sub(int a, int b) {
	return (a - b + MOD) % MOD;
}

int mul(int a, int b) {
	return 1LL * a * b % MOD;
}

int bin_pow(int a, int p) {
	int res = 1;
	while (p) {
		if (p & 1)
			res = mul(res, a);
		a = mul(a, a);
		p >>= 1;
	}
	return res;
}

int diw(int a, int b) {
	return mul(a, bin_pow(b, MOD - 2));
}

int c(int n, int k) {
	int dw = mul(fact[k], fact[n - k]);
	return diw(fact[n], dw);
}

void gen(string s) {
	if (size(s) == 2) {
		int cnt = 0;
		cnt += s[0] == 'a';
		cnt += s[1] == 'a';
		if (cnt == 1)
			cout << s << endl;
		return;
	}
	for (char c = 'a'; c <= 'z'; c++)
		gen(s + c);
}

void solve() {
	fact[0] = 1;
	for (int i = 1; i < N; i++)
		fact[i] = mul(fact[i - 1], i);
	cin >> k >> s;
	int dp = 0, ans = 0, n = size(s);
	for (int i = 0; i <= k; i++) {
		dp = mul(c(n + i - 1, n - 1), bin_pow(25, i));
		ans = add(ans, mul(dp, bin_pow(26, k - i)));
	}
	cout << ans;
}

int main() {
	double start = clock();
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
	cout << fixed << setprecision(20);
	cerr << fixed << setprecision(20);
#else
	cout << fixed << setprecision(20);
	ios_base::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	rnd.seed(time(0));
#endif
		
	int t = 1;
	for (int i = 0; i < t; i++) {
		solve();
	}

#ifdef _DEBUG
	cout << endl << "Time is " << (clock() - start) / 1000.0;
#endif
}

Measured memory_bytes: 12128