#pragma GCC optimize("O2") #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include //#define int ll #define INT128_MAX (__int128)(((unsigned __int128) 1 << ((sizeof(__int128) * __CHAR_BIT__) - 1)) - 1) #define INT128_MIN (-INT128_MAX - 1) namespace R = std::ranges; namespace V = std::views; using namespace std; using ll = long long; using ull = unsigned long long; using pii = pair; using pll = pair; using tiii = tuple; using ldb = long double; //#define double ldb template ostream& operator<<(ostream& os, const pair pr) { return os << pr.first << ' ' << pr.second; } template ostream& operator<<(ostream& os, const array &arr) { for(const T &X : arr) os << X << ' '; return os; } template ostream& operator<<(ostream& os, const vector &vec) { for(const T &X : vec) os << X << ' '; return os; } /** * template name: MontgomeryModInt * author: Misuki * reference: https://github.com/NyaanNyaan/library/blob/master/modint/montgomery-modint.hpp#L10 * last update: 2023/11/30 * note: mod should be a prime less than 2^30. */ template struct MontgomeryModInt { using mint = MontgomeryModInt; using i32 = int32_t; using u32 = uint32_t; using u64 = uint64_t; static constexpr u32 get_r() { u32 res = 1, base = mod; for(i32 i = 0; i < 31; i++) res *= base, base *= base; return -res; } static constexpr u32 get_mod() { return mod; } static constexpr u32 n2 = -u64(mod) % mod; //2^64 % mod static constexpr u32 r = get_r(); //-P^{-1} % 2^32 u32 a; static u32 reduce(const u64 &b) { return (b + u64(u32(b) * r) * mod) >> 32; } static u32 transform(const u64 &b) { return reduce(u64(b) * n2); } MontgomeryModInt() : a(0) {} MontgomeryModInt(const int64_t &b) : a(transform(b % mod + mod)) {} mint pow(u64 k) const { mint res(1), base(*this); while(k) { if (k & 1) res *= base; base *= base, k >>= 1; } return res; } mint inverse() const { return (*this).pow(mod - 2); } u32 get() const { u32 res = reduce(a); return res >= mod ? res - mod : res; } mint& operator+=(const mint &b) { if (i32(a += b.a - 2 * mod) < 0) a += 2 * mod; return *this; } mint& operator-=(const mint &b) { if (i32(a -= b.a) < 0) a += 2 * mod; return *this; } mint& operator*=(const mint &b) { a = reduce(u64(a) * b.a); return *this; } mint& operator/=(const mint &b) { a = reduce(u64(a) * b.inverse().a); return *this; } mint operator-() { return mint() - mint(*this); } bool operator==(mint b) { return (a >= mod ? a - mod : a) == (b.a >= mod ? b.a - mod : b.a); } bool operator!=(mint b) { return (a >= mod ? a - mod : a) != (b.a >= mod ? b.a - mod : b.a); } friend mint operator+(mint a, mint b) { return a += b; } friend mint operator-(mint a, mint b) { return a -= b; } friend mint operator*(mint a, mint b) { return a *= b; } friend mint operator/(mint a, mint b) { return a /= b; } friend ostream& operator<<(ostream& os, const mint& b) { return os << b.get(); } friend istream& operator>>(istream& is, mint& b) { int64_t val; is >> val; b = mint(val); return is; } }; using mint = MontgomeryModInt<998244353>; /** * template name: comb * author: Misuki * last update: 2023/01/22 * note: remember to call init() before using it. */ const int MAX = 1000001; mint fac[MAX], facInv[MAX]; void init() { fac[0] = 1; for(int i = 1; i < MAX; i++) fac[i] = fac[i - 1] * i; facInv[MAX - 1] = 1 / fac[MAX - 1]; for(int i = MAX - 2; i >= 0; i--) facInv[i] = facInv[i + 1] * (i + 1); } mint C(int a, int b) { if (b < 0 or a < b) return 0; else return fac[a] * facInv[b] * facInv[a - b]; } /** * template name: NTT * reference: https://judge.yosupo.jp/submission/69896 * last update: 2023/12/04 * remark: MOD = 2^K * C + 1, R is a primitive root modulo MOD * remark: a.size() <= 2^K must be satisfied * some common modulo: 998244353 = 2^23 * 119 + 1, R = 3 * 469762049 = 2^26 * 7 + 1, R = 3 * 1224736769 = 2^24 * 73 + 1, R = 3 * verify: Library Checker - Convolution */ template struct NTT { using u32 = uint32_t; static constexpr u32 mod = (1 << k) * c + 1; static constexpr u32 get_mod() { return mod; } static void ntt(vector &a, bool inverse) { static array w, w_inv; if (w[0] == 0) { Mint root = 2; while(root.pow((mod - 1) / 2) == 1) root += 1; for(int i = 0; i < 30; i++) w[i] = -(root.pow((mod - 1) >> (i + 2))), w_inv[i] = 1 / w[i]; } int n = ssize(a); if (not inverse) { for(int m = n; m >>= 1; ) { Mint ww = 1; for(int s = 0, l = 0; s < n; s += 2 * m) { for(int i = s, j = s + m; i < s + m; i++, j++) { Mint x = a[i], y = a[j] * ww; a[i] = x + y, a[j] = x - y; } ww *= w[__builtin_ctz(++l)]; } } } else { for(int m = 1; m < n; m *= 2) { Mint ww = 1; for(int s = 0, l = 0; s < n; s += 2 * m) { for(int i = s, j = s + m; i < s + m; i++, j++) { Mint x = a[i], y = a[j]; a[i] = x + y, a[j] = (x - y) * ww; } ww *= w_inv[__builtin_ctz(++l)]; } } Mint inv = 1 / Mint(n); for(Mint &x : a) x *= inv; } } vector conv(vector a, vector b) { int sz = ssize(a) + ssize(b) - 1; int n = bit_ceil((u32)sz); a.resize(n, 0); ntt(a, false); b.resize(n, 0); ntt(b, false); for(int i = 0; i < n; i++) a[i] *= b[i]; ntt(a, true); a.resize(sz); return a; } }; NTT<23, 119, 3, mint> ntt; signed main() { ios::sync_with_stdio(false), cin.tie(NULL); init(); int n, q; cin >> n >> q; vector A(n + 1), B(n + 1); for(int i = 0; i <= n; i++) A[i] = fac[i], B[i] = facInv[n - i]; A = ntt.conv(A, B); mint ans = 0; for(int l = 1; l <= n; l++) ans += (n - l + 1) * fac[n - l] * A[l + n]; cout << ans * mint((ll)n * (n + 1) / 2).pow(q - 1) * q << '\n'; return 0; }