#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;

// chmax, chmin
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

template <typename T>
function<T(T, T)> op_max = [](T a, T b) -> T { return max(a, b); };
template <typename T>
function<T(T, T)> op_min = [](T a, T b) -> T { return min(a, b); };

template <typename T>
function<T(T, T)> op_sum = [](T a, T b) -> T { return a + b; };

namespace detail {
template <typename T, std::size_t NDIMS>
struct vector_builder {
  using type = std::vector<typename vector_builder<T, NDIMS - 1>::type>;

  static type make(std::vector<std::size_t> dims, const T& v = {}) {
    const auto vec = std::vector<T>(dims.empty() ? 0 : dims.back(), v);
    if (!dims.empty()) dims.pop_back();
    return vector_builder<std::vector<T>, NDIMS - 1>::make(dims, vec);
  }
};

template <typename T>
struct vector_builder<T, 1> {
  using type = std::vector<T>;

  static type make(std::vector<std::size_t> dims, const T& v = {}) {
    return type(dims.empty() ? 0 : dims.back(), v);
  }
};
}  // namespace detail

template <typename T, typename... SIZE_T>
auto exvector(const T& v, SIZE_T... dims) {
  static_assert(sizeof...(dims) != 0, "invalid dimension");
  std::vector<std::size_t> vec_dims{dims...};
  return detail::vector_builder<T, sizeof...(dims)>::make(vec_dims, v);
}

using namespace std;
//********************  dumps ************************//

template <typename T>
void dump(const T& data, vector<int>& iter) {
  cout << data << " ";
}
template <typename T>
void dump(const vector<T>& data, vector<int>& iter) {
  for (auto elem : data) dump(elem, iter);
  cout << endl;
}

template <typename T>
void dump(const vector<vector<T>>& data, vector<int>& iter) {
  for (auto elem : iter) {
    cout << "[" << elem << "]";
  }
  cout << endl;
  for (int i = 0; i < data.size(); i++) {
    iter.push_back(i);
    dump(data[i], iter);
    iter.pop_back();
  }
  cout << endl;
}

template <typename T>
void dump(const vector<T>& data, int dummy) {
  for (int i = 0; i < data.size(); i++) {
    cout << "[" << i << "] " << data[i] << endl;
  }
}
template <typename T>
void dump(const T& data) {  // T : data, U = base type val.
  vector<int> iter;
  dump(data, iter);
}
///////////////////////////////////////////////
const long long MOD_CONST = 1000000007;
long long mul_mod(long long a, long long b, const long long MOD) {
  return b ? (mul_mod(a * 2, b / 2, MOD) + (b & 1 ? a : 0)) % MOD : 0;
}

long long bpow_mod(long long a, long long b, const long long MOD) {
  return (b ? bpow_mod(a * a % MOD, b / 2, MOD) * (b & 1 ? a : 1) : 1) % MOD;
}

long long inv_mod(long long a, const long long MOD) {
  return bpow_mod(a, MOD - 2, MOD);
}
template <long long param = MOD_CONST, bool fast = false>
class mint {
 private:
  using Z = int;
  using N = unsigned int;
  using ZZ = long long;
  using NN = unsigned long long;
  struct {
  } constexpr static exact{};
  // Using Z deliberately to avoid Z -> N promotion.
  template <class Ret = ZZ&>
  static auto modulo() -> std::enable_if_t<(param <= 0), Ret> {
    static ZZ mod = 0;
    return mod;
  }
  template <class Ret = const ZZ>
  static auto mod() -> std::enable_if_t<(param <= 0), Ret> {
    return modulo();
  }
  template <class Ret = const ZZ>
  static constexpr auto mod() -> std::enable_if_t<(param > 0), Ret> {
    return param;
  }

 public:
  template <class Arg = ZZ>
  static void set_modulo(const std::enable_if_t<(param <= 0), Arg> mod) {
    modulo() = mod;
  }
  long long v;

  constexpr mint() : v(0) {}

  constexpr mint(long long v)
      : v(fast ? (v)
               : (v < 0 ? (v % mod() + mod()) % mod()
                        : (v >= mod() ? v % mod() : v))) {}
  constexpr long long get_mod() { return mod(); }
  long long get_val() { return v; }
  void take_mod() { v %= mod(); }
};
template <long long param, bool fast>
ostream& operator<<(ostream& os, mint<param, fast>& x) {
  return os << (x.v % x.get_mod() + x.get_mod()) % x.get_mod();
}

template <long long param, bool fast, bool fast2>
bool operator==(mint<param, fast>& a, mint<param, fast2> b) {
  return a.v == b.v;
}
template <long long param, bool fast, bool fast2>
mint<param, fast>& operator+=(mint<param, fast>& a, mint<param, fast2> b) {
  return a = a.v + b.v;
}
template <long long param>
mint<param>& operator-=(mint<param>& a, mint<param> b) {
  return a = a.v - b.v;
}
template <long long param>
mint<param>& operator*=(mint<param>& a, mint<param> b) {
  return a = a.v * b.v;
}
template <long long param>
mint<param>& operator/=(mint<param>& a, mint<param> b) {
  return a = a.v * inv_mod(b.v, a.get_mod());
}
template <long long param, bool fast, bool fast2>
mint<param, fast> operator+(mint<param, fast> a, mint<param, fast2> b) {
  return a += b;
}
template <long long param>
mint<param> operator-(mint<param> a, mint<param> b) {
  return a -= b;
}
template <long long param>
mint<param> operator*(mint<param> a, mint<param> b) {
  return a *= b;
}
template <long long param>
mint<param> operator/(mint<param> a, mint<param> b) {
  return a /= b;
}
template <long long param, bool fast>
mint<param, fast>& operator+=(mint<param, fast>& a, long long b) {
  return a = a.v + b;
}
template <long long param>
mint<param>& operator-=(mint<param>& a, long long b) {
  return a = a.v - b;
}
template <long long param>
mint<param>& operator*=(mint<param>& a, long long b) {
  return a = a.v * b;
}
template <long long param>
mint<param>& operator/=(mint<param>& a, long long b) {
  return a = a.v * inv_mod(b, a.get_mod());
}
template <long long param, bool fast>
mint<param, fast> operator+(mint<param> a, long long b) {
  return a += b;
}
template <long long param>
mint<param> operator-(mint<param> a, long long b) {
  return a -= b;
}
template <long long param>
mint<param> operator*(mint<param> a, long long b) {
  return a *= b;
}
template <long long param>
mint<param> operator/(mint<param> a, long long b) {
  return a /= b;
}
template <int size = 400000, long long param = MOD_CONST, bool preserve = false>
class CombinationTool {
  vector<mint<param>> invs;

 public:
  vector<mint<param>> kaijo;
  vector<vector<mint<param>>> table;

  CombinationTool() {
    int N = size;
    if (preserve) {
      table.resize(N + 5);
      for (int i = 0; i < N + 5; i++) table[i].resize(i + 1);
      for (int i = 0; i < N; i++) {
        table[i][0] = 1;
        table[i][i] = 1;
      }
      for (int i = 1; i < N + 5; i++)
        for (int j = 1; j < i; j++)
          table[i][j] = table[i - 1][j - 1] + table[i - 1][j];

    } else {
      kaijo.resize(N + 5);
      invs.resize(N + 5);
      kaijo[0] = 1;
      invs[0] = 1;
      for (int i = 1; i < N + 5; i++) {
        kaijo[i] = kaijo[i - 1] * i;
        invs[i] = mint<param>(1) / kaijo[i];
      }
    }
  }

  mint<param> get(int n, int m) {
    if (m < 0 || m > n) return mint<param>(0);
    if (preserve) return table[n][m];
    return kaijo[n] * invs[m] * invs[n - m];
  }
};

int main() {
  int n, k;
  cin >> n >> k;
  CombinationTool<> comb;

  mint<> ret = 0;
  for (int i = 0; i <= min(k, n - 1); i++) {  // number of 0
    ret += comb.get(n, i) * comb.get(n - (n - i) + (n - i - 1), n - i - 1);
    // cout << i << " " << ret << endl;
  }
  cout << ret << endl;

  return 0;
}

Measured memory_bytes: 6528