// #define MULTI_TESTCASE // #define AOJ_TESTCASE // #define FAST_CIO // #define INTERACTIVE #define INF 4'000'000'000'000'000'037LL // https://github.com/miscalculation53/library/tree/wip/template/template_all.hpp // https://github.com/miscalculation53/library/tree/wip/template/template_all_but_modint.hpp // https://github.com/miscalculation53/library/tree/wip/template/template_types.hpp #include namespace { using namespace std; using ll = long long; using uint = unsigned int; using ull = unsigned long long; using pll = pair; #define vc vector using i128 = __int128_t; using u128 = __uint128_t; #define cauto const auto // https://github.com/miscalculation53/library/tree/wip/template/template_rep.hpp #define overload4(_1,_2,_3,_4,name,...) name #define repi1(i,n) for (int i = 0, nnnnn = int(n); i < nnnnn; i++) #define repi2(i,l,r) for (int i = int(l), rrrrr = int(r); i < rrrrr; i++) #define repi(...) overload4(__VA_ARGS__, repi3, repi2, repi1)(__VA_ARGS__) #define fe(...) for (auto __VA_ARGS__) // https://github.com/miscalculation53/library/tree/wip/template/template_math.hpp // https://github.com/miscalculation53/library/tree/wip/utils/is_integral_ext.hpp template constexpr bool is_integral_ext = is_integral_v || is_same_v || is_same_v; template constexpr bool is_signed_ext = is_signed_v || is_same_v; template constexpr bool is_unsigned_ext = is_unsigned_v || is_same_v; // https://github.com/miscalculation53/library/tree/wip/utils/default_infty.hpp namespace default_infty_detail { template struct has_infty : false_type {}; template struct has_infty> : true_type {}; template const T &custom_value() { static const T value = T::infty(); return value; } template inline constexpr bool unsupported = false; } template constexpr decltype(auto) default_infty() { if constexpr (default_infty_detail::has_infty::value) return default_infty_detail::custom_value(); else if constexpr (is_same_v || is_same_v) return T(INF) * T(INF); else if constexpr (is_integral_ext && !is_same_v) { if constexpr (sizeof(T) >= sizeof(ll)) return T(INF); else if constexpr (numeric_limits::digits >= 31) return (T(1) << 30) - 1; else return T(numeric_limits::max() / 2); } else if constexpr (numeric_limits::has_infinity) return numeric_limits::infinity(); else static_assert(default_infty_detail::unsupported, "No default infinity for this type; specify infty explicitly or define T::infty()."); } template inline bool chmin(T &a, U b) { return a > b ? a = b, true : false; } template && is_integral_ext>> inline constexpr T divfloor(U a, V b) { return T(a) / T(b) - (T(a) % T(b) && (T(a) ^ T(b)) < 0); } template && is_integral_ext>> inline constexpr T safemod(U a, V b) { return T(a) - T(b) * divfloor(a, b); } template constexpr T ipow(U a, V b) { assert(b >= 0); if (b == 0) return 1; if (a == 0 || a == 1) return a; if (a < 0 && a == -1) return b & 1 ? -1 : 1; T res = 1, tmp = a; while (true) { if (b & 1) res *= tmp; b >>= 1; if (b == 0) break; tmp *= tmp; } return res; } // https://github.com/miscalculation53/library/tree/wip/template/template_vector.hpp #define ALL(a) (a).begin(), (a).end() template inline T SZ(const V &x) { return x.size(); } // https://github.com/miscalculation53/library/tree/wip/template/template_algo.hpp // https://github.com/miscalculation53/library/tree/wip/utils/resolved_infty.hpp // https://github.com/miscalculation53/library/tree/wip/utils/resolved_value.hpp template , int> = 0> constexpr T resolved_value() { return T(x); } template , long> = 0> const T &resolved_value() { static const T value = T(x()); return value; } template constexpr decltype(auto) resolved_infty() { if constexpr (is_same_v) return default_infty(); else return resolved_value(); } template struct has_e0 : false_type {}; template struct has_e0> : true_type {}; template inline constexpr bool has_e0_v = has_e0::value; namespace internal { } constexpr array DRULgrid = {{{1, 0}, {0, 1}, {-1, 0}, {0, -1}}}; constexpr array DRULplane = {{{0, -1}, {1, 0}, {0, 1}, {-1, 0}}}; // https://github.com/miscalculation53/library/tree/wip/template/template_binsearch.hpp template struct is_random_access_iterator { static constexpr bool value = is_same_v< typename iterator_traits::iterator_category, random_access_iterator_tag >; }; template constexpr bool is_random_access_iterator_v = is_random_access_iterator::value; namespace internal { }; // https://github.com/miscalculation53/library/tree/wip/template/template_bit.hpp template inline constexpr ull MASK(T k) { return (1ULL << k) - 1ULL; } inline constexpr ll countr_zero(ll x) { assert(x != 0); return std::countr_zero((ull)x); } // https://github.com/miscalculation53/library/tree/wip/template/template_inout.hpp // https://github.com/miscalculation53/library/tree/wip/template/template_dump.hpp // https://github.com/miscalculation53/library/tree/wip/template/template_dump_map.hpp #define dump(...) #define oj(...) __VA_ARGS__ namespace fastio { template struct unsigned_integer { using type = make_unsigned_t; }; template <> struct unsigned_integer { using type = u128; }; template <> struct unsigned_integer { using type = u128; }; template using unsigned_integer_t = typename unsigned_integer::type; static constexpr uint32_t SIZ = 1 << 17; char ibuf[SIZ]; char obuf[SIZ]; char out[100]; uint32_t pil = 0, pir = 0, por = 0; struct Pre { char num[10000][4]; constexpr Pre() : num() { for (int i = 0; i < 10000; i++) { int n = i; for (int j = 3; j >= 0; j--) { num[i][j] = n % 10 | '0'; n /= 10; } } } } constexpr pre; inline void load() { memcpy(ibuf, ibuf + pil, pir - pil); pir = pir - pil + fread(ibuf + pir - pil, 1, SIZ - pir + pil, stdin); pil = 0; if (pir < SIZ) ibuf[pir++] = '\n'; } inline void flush() { fwrite(obuf, 1, por, stdout); por = 0; } template void rd1_integer(T &x) { using U = unsigned_integer_t; bool minus = false; U val = 0; if constexpr (check_buffer) if (pil + 100 > pir) load(); uint32_t p = pil; while (ibuf[p] < '-') ++p; if constexpr (is_signed::value || is_same_v) { if (ibuf[p] == '-') minus = true, ++p; } while ('0' <= ibuf[p]) val = val * 10 + (ibuf[p++] & 15); pil = p; if constexpr (is_signed::value || is_same_v) { if (minus) { const U min_abs = U(numeric_limits::max()) + 1; x = val == min_abs ? numeric_limits::lowest() : -T(val); } else x = T(val); } else x = T(val); } void rd1(ll &x) { rd1_integer(x); } template void read(T &...x) { if constexpr (sizeof...(T) <= SIZ / 100 && ((!is_same_v && (is_integral_v || is_same_v || is_same_v)) && ...)) { if (pil + 100 * sizeof...(T) > pir) load(); (rd1_integer(x), ...); } else (rd1(x), ...); } void wt1(const char c) { if (por == SIZ) flush(); obuf[por++] = c; } template void wt1_integer(T x) { if (por > SIZ - 100) flush(); using U = unsigned_integer_t; U ux; if constexpr (is_signed::value || is_same_v) { if (x < 0) obuf[por++] = '-', ux = U(0) - U(x); else ux = U(x); } else ux = x; int outi; for (outi = 96; ux >= 10000; outi -= 4) { memcpy(out + outi, pre.num[ux % 10000], 4); ux /= 10000; } if (ux >= 1000) { memcpy(obuf + por, pre.num[ux], 4); por += 4; } else if (ux >= 100) { memcpy(obuf + por, pre.num[ux] + 1, 3); por += 3; } else if (ux >= 10) { int q = (ux * 103) >> 10; obuf[por] = q | '0'; obuf[por + 1] = (ux - q * 10) | '0'; por += 2; } else obuf[por++] = ux | '0'; memcpy(obuf + por, out + outi + 4, 96 - outi); por += 96 - outi; } void wt1(int x) { wt1_integer(x); } template void write(T &&...x) { (wt1(std::forward(x)), ...); } template void print(T &&...x) { if constexpr (sizeof...(T)) { int i = 0; ((i++ ? wt1(' ') : void(), wt1(std::forward(x))), ...); } wt1('\n'); } } struct Dummy { Dummy() { atexit(fastio::flush); } } dummy; namespace internal { template void READnodump(Ts &...a) { fastio::read(a...); } }; #define READ(...) internal::READnodump(__VA_ARGS__); dump(__VA_ARGS__) #define IN(T,...) T __VA_ARGS__; READ(__VA_ARGS__) #define LL(...) IN(ll, __VA_ARGS__) #define PRINT fastio::print #define PRINTRETURN(...) do { PRINT(__VA_ARGS__); return; } while (false) namespace internal { }; namespace internal { }; // https://github.com/miscalculation53/library/tree/wip/template/template_random.hpp mt19937_64 mt; template T randrange(U1 l, U2 r) { assert(T(l) < T(r)); return uniform_int_distribution(T(l), T(r) - 1)(mt); } namespace internal { }; // https://github.com/miscalculation53/library/tree/wip/math/modint/template_modint.hpp // https://github.com/miscalculation53/library/tree/wip/math/modint/modint.hpp // https://github.com/miscalculation53/library/tree/wip/math/modint/modint_internal_static.hpp // https://github.com/miscalculation53/library/tree/wip/utils/larger_int.hpp namespace larger_int_detail { } template struct larger_int { private: static constexpr bool check(); static_assert(check()); public: using type = T; }; #define LARGER_INT(T,U) template <> struct larger_int { using type = U; }; LARGER_INT(signed char, short) LARGER_INT(short, int) LARGER_INT(int, long long) LARGER_INT(long, __int128_t) LARGER_INT(long long, __int128_t) LARGER_INT(unsigned char, unsigned short) LARGER_INT(unsigned short, unsigned int) LARGER_INT(unsigned int, unsigned long long) LARGER_INT(unsigned long, __uint128_t) LARGER_INT(unsigned long long, __uint128_t) #undef LARGER_INT template struct Rational; template struct larger_int> { using type = Rational::type>; }; template using larger_int_t = typename larger_int::type; // https://github.com/miscalculation53/library/tree/wip/math/modint/modint_internal_isprime.hpp namespace internal { template constexpr ll powmod_constexpr(ll x, ll n, T m) { if (m == 1) return 0; using U = make_unsigned_t; using L = larger_int_t; U r = 1, y = safemod(x, m); while (n) { if (n & 1) r = L(r) * y % m; y = L(y) * y % m; n >>= 1; } return r; } template constexpr bool isprime_constexpr(T n) { if constexpr (sizeof(T) > 4) { if (n <= INT_MAX) return isprime_constexpr(n); } if (n <= 1) return false; if (n == 2 || n == 7 || n == 61) return true; if (n % 2 == 0) return false; ll d = n - 1; while (d % 2 == 0) d /= 2; using U = make_unsigned_t; using L = larger_int_t; auto miller_rabin = [&](const auto &bases) constexpr { for (ll a : bases) { ll t = d, y = powmod_constexpr(a, t, n); while (t != n - 1 && y != 1 && y != n - 1) { y = L(y) * y % n; t <<= 1; } if (y != n - 1 && t % 2 == 0) return false; } return true; }; if constexpr(sizeof(T) <= 4) { constexpr ll bases[3] = {2, 7, 61}; return miller_rabin(bases); } else { constexpr ll bases[7] = {2, 325, 9375, 28178, 450775, 9780504, 1795265022}; return miller_rabin(bases); } } template constexpr bool isprime = isprime_constexpr(n); }; namespace internal { template struct policy_static { using mod_type = decltype(M); using value_type = make_unsigned_t; using calc_type = larger_int_t; static constexpr bool is_prime = isprime_constexpr(M); static constexpr mod_type mod() { return M; } static constexpr value_type umod() { return M; } static constexpr value_type init(value_type v) { return v; } static constexpr mod_type val(value_type v) { return v; } static constexpr value_type mul(value_type a, value_type b) { return (value_type)((calc_type(a) * b) % M); } }; }; // https://github.com/miscalculation53/library/tree/wip/math/modint/modint_internal_barrett32.hpp namespace internal { struct barrett32 { uint m; ull im; explicit barrett32(uint m) : m(m), im((ull)(-1) / m + 1) {} uint umod() const { return m; } uint mul(uint a, uint b) const { ull z = a; z *= b; ull x = ull((u128(z) * im) >> 64); ull y = x * m; return uint(z - y + (z < y ? m : 0)); } }; template struct policy_barrett32 { using value_type = uint; using calc_type = ull; using mod_type = int; static constexpr bool is_prime = false; static inline barrett32 reducer{998244353}; static void set_mod(mod_type m) { reducer = barrett32(m); } static mod_type mod() { return reducer.umod(); } static value_type umod() { return reducer.umod(); } static value_type init(value_type v) { return v; } static mod_type val(value_type v) { return v; } static value_type mul(value_type a, value_type b) { return reducer.mul(a, b); } }; }; // https://github.com/miscalculation53/library/tree/wip/math/modint/modint_internal_montgomery64.hpp namespace internal { inline constexpr ull inv64(ull a) { ull x = a; while (a * x != 1) x *= 2 - a * x; return x; } struct montgomery64odd { ull m, im, sq; explicit montgomery64odd(ull m) : m(m), im(inv64(m)), sq(-u128(m) % m) {} ull umod() const { return m; } ull reduce(u128 x) const { auto t = (x + u128(m) * (-im * ull(x))) >> 64; if (t >= m) t -= m; return (ull)t; } ull inv_reduce(i128 v) const { return reduce(u128(v % m + m) * sq); } }; struct montgomery64 { ull m, mx, imx, d, q; uint b; explicit montgomery64(ull m) : m(m) { b = countr_zero(m), mx = m >> b; imx = inv64(mx); d = powmod_constexpr((mx + 1) / 2, b, mx); u128 sq = -u128(mx) % mx; q = (1 + (((sq - 1) * d) << b)) % m; } ull umod() const { return m; } ull reduce(u128 x) const { if (b == 0) { auto t = (x + u128(mx) * (-imx * ull(x))) >> 64; if (t >= m) t -= m; return (ull)t; } ull p = x & MASK(b); x = (x >> b) + p * d; ull y = p << (64 - b); auto t = (x + u128(mx) * (imx * (y - ull(x)))) >> (64 - b); if (t >= m) { t -= m; if (t >= m) t -= m; } return (ull)t; } ull inv_reduce(i128 v) const { return reduce(u128(v % m + m) * q); } }; template struct policy_montgomery64_odd { using value_type = ull; using calc_type = u128; using mod_type = ll; static constexpr bool is_prime = false; static inline montgomery64odd reducer{(1LL << 61) - 1}; static void set_mod(mod_type m) { reducer = montgomery64odd(m); } static mod_type mod() { return reducer.umod(); } static value_type umod() { return reducer.umod(); } static value_type init(value_type v) { return reducer.inv_reduce(v); } static mod_type val(value_type v) { return reducer.reduce(v); } static value_type mul(value_type a, value_type b) { return reducer.reduce((calc_type)a * b); } }; template struct policy_montgomery64 { using value_type = ull; using calc_type = u128; using mod_type = ll; static constexpr bool is_prime = false; static inline montgomery64 reducer{(1LL << 61) - 1}; static mod_type mod() { return reducer.umod(); } static value_type umod() { return reducer.umod(); } static value_type init(value_type v) { return reducer.inv_reduce(v); } }; }; // https://github.com/miscalculation53/library/tree/wip/math/extgcd.hpp namespace internal { template struct modint_impl { using V = typename Policy::value_type; using M = typename Policy::mod_type; using mint = modint_impl; private: V _v; public: static constexpr M mod() { return Policy::mod(); } template static auto set_mod(M m) -> decltype(T::set_mod(m)) { return T::set_mod(m); } static mint raw(V v) { mint x; x._v = v; return x; } modint_impl() : _v(0) {} template >> modint_impl(T v) { V rem; if constexpr (is_signed_ext) { using S = make_signed_t; S x = v % S(Policy::umod()); if (x < 0) x += Policy::umod(); rem = x; } else rem = V(v % Policy::umod()); _v = Policy::init(rem); }; M val() const { return Policy::val(_v); } mint &operator+=(const mint &rhs) { _v += rhs._v; if (_v >= Policy::umod()) _v -= Policy::umod(); return *this; } mint &operator-=(const mint &rhs) { _v -= rhs._v; if (_v >= Policy::umod()) _v += Policy::umod(); return *this; } mint &operator*=(const mint &rhs) { _v = Policy::mul(_v, rhs._v); return *this; } mint &operator/=(const mint &rhs) { return *this *= rhs.inv(); } mint operator-() const { return mint() - *this; } template mint pow(T n) const { assert(n >= 0); mint x = *this, r = 1; while (n) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; } mint inv() const { if constexpr (Policy::is_prime) { return pow(mod() - 2); } else { auto [g, x, y] = extgcd(val(), mod()); assert(g == 1); return mint(x); } } friend mint operator+(const mint &lhs, const mint &rhs) { return mint(lhs) += rhs; } friend mint operator-(const mint &lhs, const mint &rhs) { return mint(lhs) -= rhs; } friend mint operator*(const mint &lhs, const mint &rhs) { return mint(lhs) *= rhs; } friend mint operator/(const mint &lhs, const mint &rhs) { return mint(lhs) /= rhs; } friend bool operator==(const mint &lhs, const mint &rhs) { return lhs._v == rhs._v; } friend bool operator!=(const mint &lhs, const mint &rhs) { return lhs._v != rhs._v; } friend M safe_hash_key(const mint &x) { return x.val(); } friend void rd1(mint &x) { long long a; fastio::rd1(a); x = a; } friend void wt1(const mint &x) { fastio::wt1(x.val()); } }; }; template using static_modint32 = internal::modint_impl>; template using dynamic_modint32 = internal::modint_impl>; template using static_modint64 = internal::modint_impl>; template using dynamic_modint64_odd = internal::modint_impl>; template using dynamic_modint64 = internal::modint_impl>; using modint998244353 = static_modint32<998244353>; template struct is_modint : std::false_type { }; template struct is_modint> : std::true_type { }; template inline constexpr bool is_modint_v = is_modint::value; template struct is_static_modint : false_type {}; template struct is_static_modint> : true_type {}; template struct is_static_modint> : true_type {}; template inline constexpr bool is_static_modint_v = is_static_modint::value; template struct is_dynamic_modint : false_type {}; template struct is_dynamic_modint> : true_type {}; template struct is_dynamic_modint> : true_type {}; template struct is_dynamic_modint> : true_type {}; template inline constexpr bool is_dynamic_modint_v = is_dynamic_modint::value; // https://github.com/miscalculation53/library/tree/wip/math/modint/power_table.hpp // https://github.com/miscalculation53/library/tree/wip/math/modint/binomial.hpp template struct Binomial { private: inline static decltype(T::mod()) mod; public: inline static vc fac_, finv_, inv_; static void reserve(int n) { if constexpr (is_dynamic_modint_v) { if (mod != T::mod()) { mod = T::mod(); fac_ = {1, 1}, finv_ = {1, 1}, inv_ = {0, 1}; } } else { if (fac_.empty()) fac_ = {1, 1}, finv_ = {1, 1}, inv_ = {0, 1}; } if (n < SZ(fac_)) return; chmin(n, T::mod() - 1); int si = fac_.size(); fac_.resize(n + 1), finv_.resize(n + 1), inv_.resize(n + 1); repi(i, si, n + 1) { fac_[i] = fac_[i - 1] * T::raw(i); inv_[i] = -inv_[T::mod() % i] * T::raw(T::mod() / i); finv_[i] = finv_[i - 1] * inv_[i]; } } static T inv(int n) { n %= T::mod(); if (n < 0) n += T::mod(); assert(n != 0); reserve(n); return inv_[n]; } static T C(int n, int k) { if (n < k) return 0; if (n < 0 || k < 0) return 0; if (n >= T::mod()) return 0; reserve(n); return fac_[n] * finv_[k] * finv_[n - k]; } }; // https://github.com/miscalculation53/library/tree/wip/math/modint/stom.hpp // https://github.com/miscalculation53/library/tree/wip/math/modint/to_rational.hpp // https://github.com/miscalculation53/library/tree/wip/math/svp2d.hpp namespace cpp_dump { template struct rat_value { T p, q; friend ostream &operator<<(ostream &os, const rat_value &x) { os << x.p; if (x.q != 1) os << '/' << x.q; return os; } }; template inline constexpr bool rat_is_map = false; template inline constexpr bool rat_is_map> = true; template inline constexpr bool rat_is_map> = true; template inline constexpr bool rat_is_map> = true; template inline constexpr bool rat_is_map> = true; } using mint = modint998244353; // using mint = modint1000000007; // using mint = static_modint<1000000000>; // using mint = modint; using bi = Binomial; void init() { oj(mt.seed(random_device()())); } // https://github.com/miscalculation53/library/tree/wip/math/prime/large/factorize.hpp // https://github.com/miscalculation53/library/tree/wip/math/prime/prime_power.hpp template struct PrimePower { P p; int e; P pe; PrimePower(P p, int e = 1) : p(p), e(e), pe(ipow(p, e)) {} PrimePower(P p, int e, P pe) : p(p), e(e), pe(pe) {} }; tuple ord_pow_div(ll n, ll m) { assert(m >= 2); if (m == 2) { int e = countr_zero(n); return {e, 1LL << e, n >> e}; } if (n % m != 0) return {0, 1, n}; n /= m; if (n % m != 0) return {1, m, n}; n /= m; ll m2 = m * m; auto [f, m2f, nn] = ord_pow_div(n, m2); int e = 2 + 2 * f; ll me = m2f * m2; if (nn % m == 0) e++, me *= m, nn /= m; return {e, me, nn}; } template vc divisors(const vc> &fac) { vc res; auto dfs = [&](auto dfs, ll d, int i) -> void { if (i == SZ(fac)) { res.emplace_back(d); return; } auto &pp = fac[i]; ull nd = d; repi(j, pp.e + 1) { dfs(dfs, nd, i + 1); nd *= pp.p; } }; dfs(dfs, 1, 0); sort(ALL(res)); return res; } // https://github.com/miscalculation53/library/tree/wip/math/prime/large/primality_test.hpp namespace internal { template bool is_prime_impl(ll n, const Array &bases) { if (n <= 1) return false; if (n == 2 || n == 7 || n == 61) return true; if (n % 2 == 0) return false; ll d = (n - 1) >> countr_zero(n - 1); mint::set_mod(n); for (ll a : bases) { ll t = d; mint y = mint(a).pow(t); while (t != n - 1 && y != 1 && y != n - 1) { y *= y; t <<= 1; } if (y != n - 1 && t % 2 == 0) return false; } return true; } }; bool is_prime(ll n) { static constexpr array bases32 = {2, 7, 61}; static constexpr array bases64 = {2, 325, 9375, 28178, 450775, 9780504, 1795265022}; if (n <= INT_MAX) { using mint = dynamic_modint32; return internal::is_prime_impl(n, bases32); } else { using mint = dynamic_modint64_odd; return internal::is_prime_impl(n, bases64); } } namespace internal { template ll get_prime_factor_impl(ll n) { mint::set_mod(n); int m = pow(n, .125); while (true) { int c = randrange(1, 100); mint x = 2, y = 2, prod = 1; ll g = 1; while (g == 1) { repi(i, m) { x = x * x + c; y = y * y + c, y = y * y + c; prod *= x - y; } g = gcd(prod.val(), n); } if (g == n) continue; if (is_prime(g)) return g; else if (is_prime(n / g)) return n / g; else return get_prime_factor_impl(g); } } ll get_prime_factor(ll n) { if (n <= INT_MAX) { using mint = dynamic_modint32; return get_prime_factor_impl(n); } else { using mint = dynamic_modint64_odd; return get_prime_factor_impl(n); } } }; vc> factorize(ll n) { vc> res; repi(p, 2, 100) { if (n % p == 0) { auto [e, pe, nn] = ord_pow_div(n, p); res.emplace_back(PrimePower(p, e, pe)); n = nn; } } while (n > 1) { if (is_prime(n)) { res.emplace_back(n); break; } ll p = internal::get_prime_factor(n); auto [e, pe, nn] = ord_pow_div(n, p); res.emplace_back(PrimePower(p, e, pe)); n = nn; } sort(ALL(res), [&](const PrimePower &pp1, const PrimePower &pp2) { return pp1.p < pp2.p; }); return res; } void main2() { LL(N, M); if (M == 0) { mint ans = 0; // a == 0 and b == 0 if (N % 2 == 0) ans += bi::C(N, N / 2) * bi::C(N, N / 2); // a == 0 and b != 0 // a != 0 and b == 0 if (N % 2 == 0) ans += 2 * bi::C(N, N / 2) * (mint(2).pow(N) - bi::C(N, N / 2)); ans /= mint(4).pow(N); PRINTRETURN(ans); } auto ds = divisors(factorize(abs(M))); mint ans = 0; fe(sgn : {-1, 1}) fe(d : ds) { ll a = sgn * d, b = M / a; // 1/2 ずつの確率で a (resp. b) を +1 か -1 // +1 が k 回、-1 が N-k 回: 2k-N if ((a + N) % 2 != 0 || (b + N) % 2 != 0) continue; ll k = (a + N) / 2, l = (b + N) / 2; mint tmp = bi::C(N, k) * bi::C(N, l); ans += tmp; dump(a, b, k, l, tmp); } ans /= mint(4).pow(N); PRINT(ans); } void test() { } // https://github.com/miscalculation53/library/tree/wip/template/template_main.hpp template struct Main { Main() { cauto CERR = [](string val, string color) { string s = "\033[" + color + "m" + val + "\033[m"; }; CERR("\n[FAST_IO]\n\n", "32"); cout << fixed << setprecision(20); init(); CERR("\n[SINGLE_TESTCASE]\n\n", "36"); main2(); } }; Main main_dummy; } int main() {}