#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 using namespace std; #define SZ(x) (int)(x.size()) #define REP(i, n) for(int i=0;i=0;--i) #define RFOR(i, a, b) for(int i=b-1;i>=a;--i) #define all(x) begin(x),end(x) #define dump(x) cerr<<#x<<" = "<<(x)<; using vvi = vector; using vll = vector; using vvll = vector; using P = pair; const double eps = 1e-8; const ll MOD = 1000000007; const int INF = INT_MAX / 2; const ll LINF = LLONG_MAX / 2; template bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; } template bool chmin(T &a, const T &b) { if (b < a) { a = b; return true; } return false; } template ostream &operator<<(ostream &os, const pair p) { os << p.first << ":" << p.second; return os; } template ostream &operator<<(ostream &os, const vector &v) { os << "["; REP(i, SZ(v)) { if (i) os << ", "; os << v[i]; } return os << "]"; } // edit class Mint { using u64 = std::uint_fast64_t; u64 Modulus = MOD; public: u64 a; constexpr Mint(const u64 x = 0) noexcept : a(x % Modulus) {} constexpr u64 &value() noexcept { return a; } constexpr const u64 &value() const noexcept { return a; } constexpr Mint operator+(const Mint rhs) const noexcept { return Mint(*this) += rhs; } constexpr Mint operator-(const Mint rhs) const noexcept { return Mint(*this) -= rhs; } constexpr Mint operator*(const Mint rhs) const noexcept { return Mint(*this) *= rhs; } constexpr Mint operator/(const Mint rhs) const noexcept { return Mint(*this) /= rhs; } constexpr Mint &operator+=(const Mint rhs) noexcept { a += rhs.a; if (a >= Modulus) { a -= Modulus; } return *this; } constexpr Mint &operator-=(const Mint rhs) noexcept { if (a < rhs.a) { a += Modulus; } a -= rhs.a; return *this; } constexpr Mint &operator*=(const Mint rhs) noexcept { a = a * rhs.a % Modulus; return *this; } constexpr Mint &operator/=(Mint rhs) noexcept { u64 exp = Modulus - 2; while (exp) { if (exp % 2) { *this *= rhs; } rhs *= rhs; exp /= 2; } return *this; } constexpr Mint &pow(int rhs) noexcept { u64 exp = static_cast(rhs); Mint base(a); a = 1; while (exp) { if (exp % 2) { *this *= base; } base *= base; exp /= 2; } return *this; } }; using Int = long long; class Combination { public: vector fact; vector ifact; Combination(int n) { fact.resize(static_cast(n + 1)); ifact.resize(static_cast(n + 1)); fact[0] = ifact[0] = Mint(1); for (int i = 1; i <= n; ++i) { fact[i] = fact[i - 1] * Mint(i); ifact[i] = Mint(1) / fact[i]; } } Mint nPk(Int n, Int k) { return fact[n] * ifact[n - k]; } Mint nCk(Int n, Int k) { return fact[n] * ifact[n - k] * ifact[k]; } Mint nHk(Int n, Int k) { return nCk(n + k - 1, k - 1); } }; Combination cmb(100001); void solve() { ll N, M; cin >> N >> M; Mint ans = cmb.fact[N] / cmb.fact[N - M]; cout << ans.value() << endl; } int main() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(10); // std::ifstream in("input.txt"); // std::cin.rdbuf(in.rdbuf()); solve(); return 0; }