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Submission #14566066

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```#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;

using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vs = vector<string>;
using vld = vector<ld>;
using vvld = vector<vld>;

typedef pair<ll, ll> P;

#define bit(n) (1LL << (n))

//#define int long long

#define all(v) v.begin(), v.end()

#define rep(i, n) for (ll i = 0; i < n; i++)
#define REP(i, n) for (ll i = 1; i < n; i++)

#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define FORm(i, m) for (auto i = m.begin(); i != m.end(); i++)

template <class T>
inline void chmax(T& a, T b) {
a = std::max(a, b);
}
template <class T>
inline void chmin(T& a, T b) {
a = std::min(a, b);
}

#define mod (ll)(1e9 + 7)
// #define mod (998244353ll)

const long long INF = 1LL << 60;

// #define mod (ll)(1e9 + 7)

template <ll ModVal>
struct ModInt {
ll x;

ModInt(ll _x = 0) : x((_x % ModVal + ModVal) % ModVal) {
}

ModInt operator-() const {
return ModInt(-x);
}
ModInt& operator+=(const ModInt a) {
x += a.x;
if (x >= ModVal)
x -= ModVal;
return *this;
}
ModInt& operator-=(const ModInt a) {
x = x + ModVal - a.x;
if (x >= ModVal)
x -= ModVal;
return *this;
}
ModInt& operator*=(const ModInt a) {
x *= a.x;
x %= ModVal;
return *this;
}

ll ext_gcd(ll a, ll b, ll& x, ll& y) {
if (b == 0) {
x = 1;
y = 0;
return a;
}
ll tmp = a / b;
ll d = ext_gcd(b, a - b * tmp, y, x);
y -= tmp * x;
return d;
}

// 逆元
ModInt inv() {
ll u, v;
ext_gcd(x, ModVal, u, v);
return ModInt(u);
}

ModInt inv(const ModInt a) {
ll u, v;
ext_gcd(a.x, ModVal, u, v);
return ModInt(u);
}

ModInt& operator/=(const ModInt a) {
return (*this) *= inv(a);
}

ModInt operator+(const ModInt a) const {
ModInt retval(*this);
return retval += a;
}
ModInt operator-(const ModInt a) const {
ModInt retval(*this);
return retval -= a;
}
ModInt operator*(const ModInt a) const {
ModInt retval(*this);
return retval *= a;
}
ModInt operator/(const ModInt a) const {
ModInt retval(*this);
return retval /= a;
}

ModInt pow(ll n) {
ModInt ans(1);
while (n) {
if (n & 1)
ans = ans * x;
*this = (*this) * (*this);
n = n >> 1;
}
return ans;
}

constexpr const ll& value() {
return this->x;
}
};

template <ll ModVal>
ostream& operator<<(ostream& os, const ModInt<ModVal>& a) {
os << a.x;
return os;
}

using mint = ModInt<mod>;

template <typename T>
class Combination {
public:
Combination(ll _max_n) : max_n(_max_n), factional(max_n + 1), inv(max_n + 1) {
factional[0] = 1;
inv[0] = 1;
for (ll i = 0; i < max_n; i++) {
factional[i + 1] = factional[i] * (i + 1); // n!(mod M)
inv[i + 1] = inv[i] / (i + 1);             // k!^(M-2) (mod M)
}
}

// nCk
T choose(ll n, ll k) {
if (n == 0 && k == 0)
return 1;
if (n < k || n < 0)
return 0;
T tmp = inv[n - k] * inv[k];
return tmp * factional[n];
}

T permutation(ll n, ll k) {
if (n - k < 0) {
return 0;
}
return factional[n] / factional[n - k];
}

private:
const ll max_n;
std::vector<T> factional;
std::vector<T> inv;
};

using Comb = Combination<mint>;

using vm = vector<mint>;
using vvm = vector<vm>;
using vvvm = vector<vvm>;

signed main() {
cin.tie(0);
ios::sync_with_stdio(false);
cout << fixed << setprecision(20);

ll k;
cin >> k;
string s;
cin >> s;

// 最終的な文字列の長さ
ll n = s.size() + k;
#if 0
vvll dp(n + 1, vll(n + 1));
dp[0][0] = 1;
rep(i, n) {
rep(j, n) {
dp[i + 1][j] += dp[i][j] * 25;
dp[i + 1][j + 1] += dp[i][j];
}
}

ll ans = 0;
FOR(i, n - k, n + 1) {
ans += dp[n][i];
}

cout << ans << endl;
#endif

vm pow25(n + 10);
pow25[0] = 1;
rep(i, n + 1) {
pow25[i + 1] = pow25[i] * 25;
}

Comb C(n + 10);

mint ans = 0;
FOR(i, n - k, n + 1) {
mint ptn = 0;
ptn = C.choose(n, i) * pow25[n - i];
ans += ptn;
}

cout << ans << endl;

return 0;
}
```

#### Submission Info

Submission Time 2020-06-21 21:45:52+0900 F - Strivore spiralray C++ (GCC 9.2.1) 600 4212 Byte AC 455 ms 51228 KB

#### Judge Result

Set Name Sample Subtask1
Score / Max Score 0 / 0 600 / 600
Status
 AC × 2
 AC × 30
Set Name Test Cases
Sample sample_01.txt, sample_02.txt
Subtask1 sample_01.txt, sample_02.txt, sub1_01.txt, sub1_02.txt, sub1_03.txt, sub1_04.txt, sub1_05.txt, sub1_06.txt, sub1_07.txt, sub1_08.txt, sub1_09.txt, sub1_10.txt, sub1_11.txt, sub1_12.txt, sub1_13.txt, sub1_14.txt, sub1_15.txt, sub1_16.txt, sub1_17.txt, sub1_18.txt, sub1_19.txt, sub1_20.txt, sub1_21.txt, sub1_22.txt, sub1_23.txt, sub1_24.txt, sub1_25.txt, sub1_26.txt, sub1_27.txt, sub1_28.txt
Case Name Status Exec Time Memory
sample_01.txt 7 ms 3504 KB
sample_02.txt 10 ms 3912 KB
sub1_01.txt 444 ms 51180 KB
sub1_02.txt 447 ms 51228 KB
sub1_03.txt 445 ms 51148 KB
sub1_04.txt 455 ms 51144 KB
sub1_05.txt 40 ms 7280 KB
sub1_06.txt 151 ms 20280 KB
sub1_07.txt 176 ms 22928 KB
sub1_08.txt 219 ms 27644 KB
sub1_09.txt 216 ms 27680 KB
sub1_10.txt 220 ms 27576 KB
sub1_11.txt 147 ms 18140 KB
sub1_12.txt 91 ms 12072 KB
sub1_13.txt 229 ms 26596 KB
sub1_14.txt 76 ms 10828 KB
sub1_15.txt 25 ms 4944 KB
sub1_16.txt 17 ms 3888 KB
sub1_17.txt 3 ms 3512 KB
sub1_18.txt 2 ms 3508 KB
sub1_19.txt 2 ms 3444 KB
sub1_20.txt 267 ms 31624 KB
sub1_21.txt 200 ms 24684 KB
sub1_22.txt 296 ms 35236 KB
sub1_23.txt 157 ms 20004 KB
sub1_24.txt 322 ms 37092 KB
sub1_25.txt 223 ms 27056 KB
sub1_26.txt 131 ms 17380 KB
sub1_27.txt 268 ms 31868 KB
sub1_28.txt 90 ms 12072 KB