#define LOCAL #include using namespace std; #pragma region Macros typedef long long ll; typedef __int128_t i128; typedef unsigned int uint; typedef unsigned long long ull; #define ALL(x) (x).begin(), (x).end() template istream& operator>>(istream& is, vector& v) { for (T& x : v) is >> x; return is; } template ostream& operator<<(ostream& os, const vector& v) { for (int i = 0; i < (int)v.size(); i++) { os << v[i] << (i + 1 == (int)v.size() ? "" : " "); } return os; } template ostream& operator<<(ostream& os, const pair& p) { os << '(' << p.first << ',' << p.second << ')'; return os; } template ostream& operator<<(ostream& os, const map& m) { os << '{'; for (auto itr = m.begin(); itr != m.end();) { os << '(' << itr->first << ',' << itr->second << ')'; if (++itr != m.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const unordered_map& m) { os << '{'; for (auto itr = m.begin(); itr != m.end();) { os << '(' << itr->first << ',' << itr->second << ')'; if (++itr != m.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const set& s) { os << '{'; for (auto itr = s.begin(); itr != s.end();) { os << *itr; if (++itr != s.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const multiset& s) { os << '{'; for (auto itr = s.begin(); itr != s.end();) { os << *itr; if (++itr != s.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const unordered_set& s) { os << '{'; for (auto itr = s.begin(); itr != s.end();) { os << *itr; if (++itr != s.end()) os << ','; } os << '}'; return os; } template ostream& operator<<(ostream& os, const deque& v) { for (int i = 0; i < (int)v.size(); i++) { os << v[i] << (i + 1 == (int)v.size() ? "" : " "); } return os; } template void print_tuple(ostream&, const T&) {} template void print_tuple(ostream& os, const T& t) { if (i) os << ','; os << get(t); print_tuple(os, t); } template ostream& operator<<(ostream& os, const tuple& t) { os << '{'; print_tuple<0, tuple, Args...>(os, t); return os << '}'; } void debug_out() { cerr << '\n'; } template void debug_out(Head&& head, Tail&&... tail) { cerr << head; if (sizeof...(Tail) > 0) cerr << ", "; debug_out(move(tail)...); } #ifdef LOCAL #define debug(...) \ cerr << " "; \ cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]" << '\n'; \ cerr << " "; \ debug_out(__VA_ARGS__) #else #define debug(...) 42 #endif template T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; } template T lcm(T x, T y) { return x / gcd(x, y) * y; } int topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); } int topbit(long long t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); } int botbit(signed a) { return a == 0 ? 32 : __builtin_ctz(a); } int botbit(long long a) { return a == 0 ? 64 : __builtin_ctzll(a); } int popcount(signed t) { return __builtin_popcount(t); } int popcount(long long t) { return __builtin_popcountll(t); } bool ispow2(int i) { return i && (i & -i) == i; } template T ceil(T x, T y) { assert(y >= 1); return (x > 0 ? (x + y - 1) / y : x / y); } template T floor(T x, T y) { assert(y >= 1); return (x > 0 ? x / y : (x - y + 1) / y); } template inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return true; } return false; } #pragma endregion #include #include #include template class modint { using i64 = int64_t; using u32 = uint32_t; using u64 = uint64_t; static_assert(Modulus < static_cast(1) << 31, "Modulus must be less than 2**31"); static constexpr u32 mod = Modulus; u32 v; public: constexpr modint(const i64 x = 0) noexcept : v(x < 0 ? mod - 1 - (-(x + 1) % mod) : x % mod) {} constexpr u32& value() noexcept { return v; } constexpr const u32& value() const noexcept { return v; } constexpr modint operator+(const modint& rhs) const noexcept { return modint(*this) += rhs; } constexpr modint operator-(const modint& rhs) const noexcept { return modint(*this) -= rhs; } constexpr modint operator*(const modint& rhs) const noexcept { return modint(*this) *= rhs; } constexpr modint operator/(const modint& rhs) const noexcept { return modint(*this) /= rhs; } constexpr modint& operator+=(const modint& rhs) noexcept { v += rhs.v; if (v >= mod) v -= mod; return *this; } constexpr modint& operator-=(const modint& rhs) noexcept { if (v < rhs.v) v += mod; v -= rhs.v; return *this; } constexpr modint& operator*=(const modint& rhs) noexcept { v = (u64)v * rhs.v % mod; return *this; } constexpr modint& operator/=(const modint& rhs) noexcept { return *this *= rhs.inv(); } constexpr modint pow(long long n) const noexcept { assert(0 <= n); modint self(*this), res(1); while (n > 0) { if (n & 1) res *= self; self *= self; n >>= 1; } return res; } constexpr modint inv() const noexcept { assert(*this != 0); return pow(mod - 2); } constexpr modint& operator++() noexcept { if (++v == mod) v = 0; return *this; } constexpr modint& operator--() noexcept { if (v == 0) v = mod; return --v, *this; } constexpr modint operator++(int) noexcept { modint t = *this; return ++*this, t; } constexpr modint operator--(int) noexcept { modint t = *this; return --*this, t; } constexpr modint operator-() const noexcept { return modint(mod - v); } template friend constexpr modint operator+(T x, modint y) noexcept { return modint(x) + y; } template friend constexpr modint operator-(T x, modint y) noexcept { return modint(x) - y; } template friend constexpr modint operator*(T x, modint y) noexcept { return modint(x) * y; } template friend constexpr modint operator/(T x, modint y) noexcept { return modint(x) / y; } constexpr bool operator==(const modint& rhs) const noexcept { return v == rhs.v; } constexpr bool operator!=(const modint& rhs) const noexcept { return v != rhs.v; } constexpr bool operator!() const noexcept { return !v; } friend std::istream& operator>>(std::istream& s, modint& rhs) noexcept { i64 v; rhs = modint{(s >> v, v)}; return s; } friend std::ostream& operator<<(std::ostream& s, const modint& rhs) noexcept { return s << rhs.v; } }; /** * @brief modint * @docs docs/modulo/modint.md */ /** * @brief ラグランジュ補間 * @docs docs/polynomial/lagrange_interpolation.md */ template M lagrange_interpolation(vector x, vector y, M T) { int n = x.size() - 1; M res = 0; for (int i = 0; i <= n; i++) { M c = 1; for (int j = 0; j <= n; j++) { if (i == j) continue; (c *= T - x[j]) /= x[i] - x[j]; } res += c * y[i]; } return res; } template M lagrange_interpolation_arithmetic(vector& y, M T) { int n = y.size() - 1; if (T.value() <= n) return y[T.value()]; vector left(n + 1, 1), right(n + 1, 1), fac(n + 1, 1), finv(n + 1, 1); for (int i = 0; i < n; i++) left[i + 1] = left[i] * (T - i); for (int i = n - 1; i >= 0; --i) right[i] = right[i + 1] * (T - (i + 1)); for (int i = 1; i <= n; i++) fac[i] = fac[i - 1] * i; finv[n] = (M)1 / fac[n]; for (int i = n; i > 0; --i) finv[i - 1] = finv[i] * i; M res = 0; for (int i = 0; i <= n; i++) { M add = y[i] * left[i] * right[i] * finv[i] * finv[n - i]; if ((n - i) & 1) res -= add; else res += add; } return res; } const int INF = 1e9; const long long IINF = 1e18; const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1}; const char dir[4] = {'D', 'R', 'U', 'L'}; const long long MOD = 1000000007; // const long long MOD = 998244353; using mint = modint<1000000007>; int main() { cin.tie(0); ios::sync_with_stdio(false); long long n; int k; cin >> n >> k; vector A(k + 2, 0); for (int i = 1; i <= k + 1; i++) A[i] = A[i - 1] + ((mint)i).pow(k); cout << lagrange_interpolation_arithmetic(A, (mint)n) << '\n'; return 0; }