#line 2 "library/KowerKoint/base.hpp" #ifndef ONLINE_JUDGE #define _GLIBCXX_DEBUG #endif #include using namespace std; #define REP(i, n) for(int i = 0; i < (int)(n); i++) #define FOR(i, a, b) for(ll i = a; i < (ll)(b); i++) #define ALL(a) (a).begin(),(a).end() #define END(...) { print(__VA_ARGS__); return; } using VI = vector; using VVI = vector; using VVVI = vector; using ll = long long; using VL = vector; using VVL = vector; using VVVL = vector; using VD = vector; using VVD = vector; using VVVD = vector; using VS = vector; using VVS = vector; using VVVS = vector; using VC = vector; using VVC = vector; using VVVC = vector; using P = pair; using VP = vector

; using VVP = vector; using VVVP = vector; using LP = pair; using VLP = vector; using VVLP = vector; using VVVLP = vector; template using PQ = priority_queue; template using GPQ = priority_queue, greater>; constexpr int INF = 1001001001; constexpr ll LINF = 1001001001001001001ll; constexpr int DX[] = {1, 0, -1, 0}; constexpr int DY[] = {0, 1, 0, -1}; void print() { cout << '\n'; } template void print(const T &t) { cout << t << '\n'; } template void print(const Head &head, const Tail &... tail) { cout << head << ' '; print(tail...); } #ifdef ONLINE_JUDGE template void dbg(const Args &... args) {} #else void dbg() { cerr << '\n'; } template void dbg(const T &t) { cerr << t << '\n'; } template void dbg(const Head &head, const Tail &... tail) { cerr << head << ' '; dbg(tail...); } #endif template< typename T1, typename T2 > ostream &operator<<(ostream &os, const pair< T1, T2 >& p) { os << p.first << " " << p.second; return os; } template< typename T1, typename T2 > istream &operator>>(istream &is, pair< T1, T2 > &p) { is >> p.first >> p.second; return is; } template< typename T > ostream &operator<<(ostream &os, const vector< T > &v) { for(int i = 0; i < (int) v.size(); i++) { os << v[i] << (i + 1 != (int) v.size() ? " " : ""); } return os; } template< typename T > istream &operator>>(istream &is, vector< T > &v) { for(T &in : v) is >> in; return is; } template vector> split(typename vector::const_iterator begin, typename vector::const_iterator end, T val) { vector> res; vector cur; for(auto it = begin; it != end; it++) { if(*it == val) { res.push_back(cur); cur.clear(); } else cur.push_back(val); } res.push_back(cur); return res; } vector split(typename string::const_iterator begin, typename string::const_iterator end, char val) { vector res; string cur = ""; for(auto it = begin; it != end; it++) { if(*it == val) { res.push_back(cur); cur.clear(); } else cur.push_back(val); } res.push_back(cur); return res; } template< typename T1, typename T2 > inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); } template< typename T1, typename T2 > inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); } template pair> compress(const vector &a) { int n = a.size(); vector x; REP(i, n) x.push_back(a[i]); sort(ALL(x)); x.erase(unique(ALL(x)), x.end()); VI res(n); REP(i, n) res[i] = lower_bound(ALL(x), a[i]) - x.begin(); return make_pair(res, x); } template pair, vector> factorial(int n) { vector res(n+1), rev(n+1); res[0] = 1; REP(i, n) res[i+1] = res[i] * (i+1); rev[n] = 1 / res[n]; for(int i = n; i > 0; i--) { rev[i-1] = rev[i] * i; } return make_pair(res, rev); } #line 2 "library/KowerKoint/test/yukicoder-391/main.cpp" /* #include */ /* using namespace atcoder; */ /* #include "KowerKoint/expansion/ac-library/all.hpp" */ #line 3 "library/KowerKoint/internal_operator.hpp" namespace internal_operator { template T default_add(T a, T b) { return a + b; } template T default_sub(T a, T b) { return a - b; } template T zero() { return T(0); } template T default_div(T a, T b) { return a / b; } template T default_mult(T a, T b) { return a * b; } template T one() { return T(1); } template T default_xor(T a, T b) { return a ^ b; } template T default_and(T a, T b) { return a & b; } template T default_or(T a, T b) { return a | b; } ll mod3() { return 998244353LL; } ll mod7() { return 1000000007LL; } ll mod9() { return 1000000009LL; } } #line 3 "library/KowerKoint/integer.hpp" VL divisor(ll n) { assert(n > 0); VL fow, bck; for(ll i = 1; i * i <= n; i++) { if(n % i == 0) { fow.push_back(i); if(i * i != n) bck.push_back(n / i); } } reverse(ALL(bck)); fow.insert(fow.end(), ALL(bck)); return fow; } bool is_prime(ll n) { assert(n > 0); for(ll d = 2; d*d <= n; d++) { if(n % d == 0) return false; } return true; } VL least_prime_factors(ll n) { assert(n > 0); VL lpfs(n+1, -1), primes; FOR(d, 2, n+1) { if(lpfs[d] == -1) { lpfs[d] = d; primes.push_back(d); } for(ll p : primes) { if(p * d > n || p > lpfs[d]) break; lpfs[p*d] = p; } } return lpfs; } VL prime_list(ll n) { assert(n > 0); VL primes; vector sieved(n+1); FOR(d, 2, n+1) { if(!sieved[d]) { primes.push_back(d); for(ll i = d*d; i <= n; i += d) sieved[i] = 1; } } return primes; } map prime_factor(ll n) { assert(n > 0); map factor; for(ll d = 2; d*d <= n; d++) { while(n%d == 0) { n /= d; factor[d]++; } } if(n > 1) factor[n]++; return factor; } ll extgcd(ll a, ll b, ll& x, ll& y) { x = 1, y = 0; ll nx = 0, ny = 1; while(b) { ll q = a / b; tie(a, b) = LP(b, a % b); tie(x, nx) = LP(nx, x - nx*q); tie(y, ny) = LP(ny, y - ny*q); } return a; } ll inv_mod(ll n, ll m) { ll x, y; assert(extgcd(n, m, x, y) == 1); x %= m; if(x < 0) x += m; return x; } ll pow_mod(ll a, ll n, ll m) { if(n == 0) return 1LL; if(n < 0) return inv_mod(pow_mod(a, -n, m), m); ll res = 1; while(n) { if(n & 1) { res *= a; res %= m; } n >>= 1; a *= a; a %= m; } return res; } #line 5 "library/KowerKoint/modint.hpp" template struct Modint { ll val; Modint(): val(0) {} Modint(ll x): val(x) { val %= mod(); if(val < 0) val += mod(); } Modint& operator+=(const Modint& r) { val += r.val; if(val >= mod()) val -= mod(); return *this; } friend Modint operator+(const Modint& l, const Modint& r) { return Modint(l) += r; } Modint& operator-=(const Modint& r) { val -= r.val; if(val < mod()) val += mod(); return *this; } friend Modint operator-(const Modint& l, const Modint& r) { return Modint(l) -= r; } Modint& operator*=(const Modint& r) { val *= r.val; val %= mod(); return *this; } Modint operator*(const Modint& r) { return (Modint(*this) *= r); } friend Modint operator*(const Modint& l, const Modint& r) { return Modint(l) *= r; } Modint pow(ll n) const { return Modint(pow_mod(val, n, mod())); } Modint inv() const { return Modint(inv_mod(val, mod())); } Modint& operator/=(const Modint& r) { return (*this *= r.inv()); } friend Modint operator/(const Modint& l, const Modint& r) { return Modint(l) /= r; } Modint& operator^=(const ll n) { val = pow_mod(val, n, mod()); return *this; } Modint operator^(const ll n) { return this->pow(n); } Modint operator+() const { return *this; } Modint operator-() const { return Modint() - *this; } Modint& operator++() { val++; if(val == mod()) val = 0LL; return *this; } Modint& operator++(int) { Modint res(*this); ++*this; return res; } Modint& operator--() { if(val == 0LL) val = mod(); val--; return *this; } Modint& operator--(int) { Modint res(*this); --*this; return res; } friend bool operator==(const Modint& l, const Modint& r) { return l.val == r.val; } friend bool operator!=(const Modint& l, const Modint& r) { return l.val != r.val; } static pair, vector> factorial(int n) { vector fact(n+1), rfact(n+1); fact[0] = 1; REP(i, n) fact[i+1] = fact[i] * (i+1); rfact[n] = 1 / fact[n]; for(int i = n-1; i >= 0; i--) rfact[i] = rfact[i+1] * (i+1); return {fact, rfact}; } friend istream& operator>>(istream& is, Modint& mi) { is >> mi.val; return is; } friend ostream& operator<<(ostream& os, const Modint& mi) { os << mi.val; return os; } }; using MI3 = Modint; using V3 = vector; using VV3 = vector; using VVV3 = vector; using MI7 = Modint; using V7 = vector; using VV7 = vector; using VVV7 = vector; using MI9 = Modint; using V9 = vector; using VV9 = vector; using VVV9 = vector; #line 3 "library/KowerKoint/counting.hpp" template struct Counting { vector fact, ifact; Counting() {} void expand(ll n) { ll sz = (ll)fact.size(); if(sz > n) return; fact.resize(n+1); ifact.resize(n+1); fact[0] = 1; FOR(i, max(1LL, sz), n+1) fact[i] = fact[i-1] * i; ifact[n] = 1 / fact[n]; for(ll i = n-1; i >= sz; i--) ifact[i] = ifact[i+1] * (i+1); } T permutation(ll n, ll r) { assert(n >= r); assert(r >= 0); expand(n); return fact[n] * ifact[n-r]; } T combination(ll n, ll r) { assert(n >= r); assert(r >= 0); expand(n); return fact[n] * ifact[r] * ifact[n-r]; } T stirling(ll n, ll k) { assert(n >= k); assert(k >= 0); if(n == 0) return 1; T res = 0; int sign = k%2? -1 : 1; expand(k); REP(i, k+1) { res += sign * ifact[i] * ifact[k-i] * T(i).pow(n); sign *= -1; } return res; } vector> stirling_table(ll n, ll k) { assert(n >= 0 && k >= 0); vector> res(n+1, vector(k+1)); res[0][0] = 1; FOR(i, 1, n+1) FOR(j, 1, k+1) { res[i][j] = res[i-1][j-1] + j * res[i-1][j]; } return res; } T bell(ll n, ll k) { assert(n >= k); assert(k >= 0); expand(k); vector tmp(k+1); int sign = 1; tmp[0] = 1; FOR(i, 1, k+1) { sign *= -1; tmp[i] = tmp[i-1] + sign * ifact[i]; } T res = 0; REP(i, k+1) { res += T(i).pow(n) * ifact[i] * tmp[k-i]; } return res; } vector> partition_table(ll n, ll k) { vector> res(n+1, vector(k+1)); res[0][0] = 1; FOR(i, 1, n+1) FOR(j, 1, i+1) { res[i][j] = res[i][j-1] + res[i-j][j]; } return res; } }; #line 8 "library/KowerKoint/test/yukicoder-391/main.cpp" void solve(){ ll n, m; cin >> n >> m; if(n < m) { print(0); return; } Counting counting; counting.expand(m); print(counting.stirling(n, m) * counting.fact[m]); } // generated by oj-template v4.7.2 (https://github.com/online-judge-tools/template-generator) int main() { // Fasterize input/output script ios::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(100); // scanf/printf user should delete this fasterize input/output script int t = 1; //cin >> t; // comment out if solving multi testcase for(int testCase = 1;testCase <= t;++testCase){ solve(); } return 0; }