#include #define NTT_MAX 20 #define NTT_d_MAX (1 << NTT_MAX) const int Mod = 998244353, bit[24] = {1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608}, bit_inv[24] = {1, 499122177, 748683265, 873463809, 935854081, 967049217, 982646785, 990445569, 994344961, 996294657, 997269505, 997756929, 998000641, 998122497, 998183425, 998213889, 998229121, 998236737, 998240545, 998242449, 998243401, 998243877, 998244115, 998244234}, root[24] = {1, 998244352, 911660635, 372528824, 929031873, 452798380, 922799308, 781712469, 476477967, 166035806, 258648936, 584193783, 63912897, 350007156, 666702199, 968855178, 629671588, 24514907, 996173970, 363395222, 565042129, 733596141, 267099868, 15311432}, root_inv[24] = {1, 998244352, 86583718, 509520358, 337190230, 87557064, 609441965, 135236158, 304459705, 685443576, 381598368, 335559352, 129292727, 358024708, 814576206, 708402881, 283043518, 3707709, 121392023, 704923114, 950391366, 428961804, 382752275, 469870224}; void NTT_inline(int kk, int a[], int x[]) { int h, hh, i, ii, j, jj, k, l, r = bit[kk], d = bit[kk-1], tmpp, cur, prev; int *pi, *pii, *pj, *pjj; static int y[2][NTT_d_MAX]; long long tmp; for (i = 0; i < r; i++) y[0][i] = a[i]; for (k = 1, kk--, cur = 1, prev = 0; kk >= 0; k++, kk--, cur ^= 1, prev ^= 1) { for (h = 0, tmp = 1; h << (kk + 1) < r; h++, tmp = tmp * root[k] % Mod) { for (hh = 0, pi = &(y[cur][h<= Mod) *pi -= Mod; *pii = *pj - tmpp; if (*pii < 0) *pii += Mod; } } } for (i = 0; i < r; i++) x[i] = y[prev][i]; } void NTT_reverse_inline(int kk, int a[], int x[]) { int h, hh, i, ii, j, jj, k, l, r = bit[kk], d = bit[kk-1], tmpp, cur, prev; int *pi, *pii, *pj, *pjj; static int y[2][NTT_d_MAX]; long long tmp; for (i = 0; i < r; i++) y[0][i] = a[i]; for (k = 1, kk--, cur = 1, prev = 0; kk >= 0; k++, kk--, cur ^= 1, prev ^= 1) { for (h = 0, tmp = 1; h << (kk + 1) < r; h++, tmp = tmp * root_inv[k] % Mod) { for (hh = 0, pi = &(y[cur][h<= Mod) *pi -= Mod; *pii = *pj - tmpp; if (*pii < 0) *pii += Mod; } } } for (i = 0; i < r; i++) x[i] = y[prev][i]; } #define NTT_THR 70 // Compute c[0-dc] = a[0-da] * b[0-db] (naive) void FPS_prod_naive(int da, int db, int dc, int a[], int b[], int c[]) { int i, j, sa, sb; static int supp_a[NTT_d_MAX], supp_b[NTT_d_MAX]; static long long tmp[NTT_d_MAX]; for (i = 0, sa = 0; i <= da; i++) if (a[i] != 0) supp_a[sa++] = i; for (i = 0, sb = 0; i <= db; i++) if (b[i] != 0) supp_b[sb++] = i; for (i = 0; i <= dc; i++) tmp[i] = 0; for (i = 0; i < sa; i++) for (j = 0; j < sb && supp_a[i] + supp_b[j] <= dc; j++) tmp[supp_a[i] + supp_b[j]] += (long long)a[supp_a[i]] * b[supp_b[j]] % Mod; for (i = 0; i <= dc; i++) c[i] = tmp[i] % Mod; } // Compute c[0-dc] = a[0-da] * b[0-db] (NTT) void FPS_prod_NTT(int da, int db, int dc, int a[], int b[], int c[]) { int i, k; static int aa[NTT_d_MAX], bb[NTT_d_MAX], cc[NTT_d_MAX]; for (k = 0; bit[k] <= da + db; k++); for (i = 0; i <= da; i++) aa[i] = a[i]; for (i = da + 1; i < bit[k]; i++) aa[i] = 0; for (i = 0; i <= db; i++) bb[i] = b[i]; for (i = db + 1; i < bit[k]; i++) bb[i] = 0; static int x[NTT_d_MAX], y[NTT_d_MAX], z[NTT_d_MAX]; NTT_inline(k, aa, x); if (db == da) { for (i = 0; i <= da; i++) if (a[i] != b[i]) break; if (i <= da) NTT_inline(k, bb, y); else for (i = 0; i < bit[k]; i++) y[i] = x[i]; } else NTT_inline(k, bb, y); for (i = 0; i < bit[k]; i++) z[i] = (long long)x[i] * y[i] % Mod; NTT_reverse_inline(k, z, cc); for (i = 0; i <= dc; i++) c[i] = (long long)cc[i] * bit_inv[k] % Mod; } // Compute c[0-dc] = a[0-da] * b[0-db] void FPS_prod(int da, int db, int dc, int a[], int b[], int c[]) { int i, sa, sb; if (da > dc) da = dc; if (db > dc) db = dc; for (i = 0, sa = 0; i <= da && sa <= NTT_THR; i++) if (a[i] != 0) sa++; for (i = 0, sb = 0; i <= db && sb <= NTT_THR; i++) if (b[i] != 0) sb++; if (sa <= NTT_THR || sb <= NTT_THR) FPS_prod_naive(da, db, dc, a, b, c); else FPS_prod_NTT(da, db, dc, a, b, c); } void solve_recursion(int l, int r, long long ans[], int coeff[]) { if (l == r) { ans[l] %= Mod; return; } int i, m = (l + r) / 2; static int a[200001], b[200001]; solve_recursion(l, m, ans, coeff); for (i = 0; i <= m - l; i++) a[i] = ans[i+l]; FPS_prod(m - l, r - l, r - l, a, coeff, b); for (i = m - l; i < r - l; i++) ans[i+l+1] += b[i]; solve_recursion(m + 1, r, ans, coeff); } long long solve(int n, long long m) { int i, coeff[200001] = {}; long long ans[200001] = {1}; for (i = 0; i <= n && i < m; i++) { switch (i % 6) { case 0: case 1: coeff[i] = (m - i) % Mod; break; case 3: case 4: coeff[i] = (Mod - (m - i) % Mod) % Mod; break; } } solve_recursion(0, n, ans, coeff); return ans[n]; } int main() { int n; long long m; scanf("%d %lld", &n, &m); printf("%lld\n", solve(n, m)); fflush(stdout); return 0; }