#include <bits/stdc++.h>
using longlong=long long;

template <typename T>
T inverse(T a, T m) {
    T u = 0, v = 1;
    while (a != 0) {
        T t = m / a;
        m -= t * a; std::swap(a, m);
        u -= t * v; std::swap(u, v);
    }
    assert(m == 1);
    return u;
}
template <typename T>
class modular {
    private:
        int value;
    public:
        constexpr modular() = default;
        constexpr modular(const modular&) = default;
        constexpr modular(modular&&) = default;
        modular& operator=(const modular&) = default;
        modular& operator=(modular&&) = default;

        template <typename U>
        modular (const U& x) {value = normalize(x);}

        template <typename U>
        static auto normalize(const U& x) {
            int v = static_cast<int>(-mod() <= x && x < mod() ? x : x % mod());
            if (v < 0) v += mod();
            return v;
        }

        auto const& operator()() const { return value; }
        template <typename U>
        explicit operator U() const { return static_cast<U>(value); }
        constexpr static auto mod() { return T::value; }

        auto& operator+=(const modular& other) {
            if ((value += other.value) >= mod()) value -= mod();
            return *this;
        }
        auto& operator-=(const modular& other) {
            if ((value -= other.value) < 0) value += mod();
            return *this;
        }
        template <typename U>
        auto& operator+=(const U& other) {return *this += modular(other); }
        template <typename U>
        auto& operator-=(const U& other) {return *this -= modular(other); }
        auto operator-() const { return modular(-value); }
        auto& operator++() {return *this += 1;}
        auto& operator--() {return *this -= 1;}
        auto    operator++(int) {modular result(*this); operator++(); return result;}
        auto    operator--(int) {modular result(*this); operator--(); return result;}

        template <typename U = T>
        auto& operator*=(const modular& rhs) {
            value = normalize(static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value));
            return *this;
        }
        auto& operator/=(const modular& other) {
            return *this *= modular(inverse(other.value, mod()));
        }
};
template <typename T> struct is_modular : std::false_type {};
template <typename T> struct is_modular <modular<T>> : std::true_type{};
template <typename T> constexpr bool is_modular_v = is_modular<T>::value;

template <typename T> bool operator==(const modular<T>& lhs, const modular<T>& rhs) { return lhs() == rhs(); }
template <typename T, typename U> bool operator==(const modular<T>& lhs, U rhs) { return lhs == modular<T>(rhs); }
template <typename T, typename U> bool operator==(U lhs, const modular<T>& rhs) { return modular<T>(lhs) == rhs; }

template <typename T> bool operator!=(const modular<T>& lhs, const modular<T>& rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(const modular<T>& lhs, U rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(U lhs, const modular<T>& rhs) { return !(lhs == rhs); }

template <typename T> modular<T> operator+(const modular<T>& lhs, const modular<T>& rhs) { return modular<T>(lhs) += rhs; }
template <typename T, typename U> modular<T> operator+(const modular<T>& lhs, U rhs) { return modular<T>(lhs) += rhs; }
template <typename T, typename U> modular<T> operator+(U lhs, const modular<T>& rhs) { return modular<T>(lhs) += rhs; }

template <typename T> modular<T> operator-(const modular<T>& lhs, const modular<T>& rhs) { return modular<T>(lhs) -= rhs; }
template <typename T, typename U> modular<T> operator-(const modular<T>& lhs, U rhs) { return modular<T>(lhs) -= rhs; }
template <typename T, typename U> modular<T> operator-(U lhs, const modular<T>& rhs) { return modular<T>(lhs) -= rhs; }

template <typename T> modular<T> operator*(const modular<T>& lhs, const modular<T>& rhs) { return modular<T>(lhs) *= rhs; }
template <typename T, typename U> modular<T> operator*(const modular<T>& lhs, U rhs) { return modular<T>(lhs) *= rhs; }
template <typename T, typename U> modular<T> operator*(U lhs, const modular<T>& rhs) { return modular<T>(lhs) *= rhs; }

template <typename T> modular<T> operator/(const modular<T>& lhs, const modular<T>& rhs) { return modular<T>(lhs) /= rhs; }
template <typename T, typename U> modular<T> operator/(const modular<T>& lhs, U rhs) { return modular<T>(lhs) /= rhs; }
template <typename T, typename U> modular<T> operator/(U lhs, const modular<T>& rhs) { return modular<T>(lhs) /= rhs; }

template<typename T, typename U>
modular<T> power (const modular<T>& a, U b) {
    assert(b >= 0);
    modular<T> x = a, ret = 1;
    for (; b > 0; b /= 2) {
        if (b % 2 == 1) ret *= x;
        x *= x;
    }
    return ret;
}

template <typename T>
std::string to_string(const modular<T>& a) {
    return std::to_string(a());
}
template <typename T>
auto operator<<(std::ostream& os, const T& a)
    -> std::enable_if_t<is_modular_v<T>, std::ostream&>{
        return os << a();
    }
template <typename T>
auto operator>>(std::istream& is, T& a)
    -> std::enable_if_t<is_modular_v<T>, std::istream&> {
    long long x; is >> x;
    a = T(x);
    return is;
}

// using mod_type = int;

// struct variable_mod { static mod_type value; };
// mod_type variable_mod::value;
// mod_type& mod = variable_mod::value;
// using mint = modular< variable_mod >;

constexpr int mod = 1'000'000'007;
using mint = modular<std::integral_constant<std::decay_t<decltype(mod)>, mod>>;

template < typename Value >
class factorials {
        std::vector< Value > fact, finv;

    public:
        factorials()=default;

        void build(int n) {
            fact.resize(n), finv.resize(n);
            fact.at(0) = 1;
            for (int i = 1; i < n; i++) fact.at(i) = fact.at(i - 1) * Value(i);
            finv.at(n - 1) = Value(1) / fact.at(n - 1);
            for (int i = n - 2; i >= 0; i--) finv.at(i) = finv.at(i + 1) * Value(i + 1);
        }
        auto operator()    (int i) const {return fact.at(i);}
        auto inv                 (int i) const {return finv.at(i);}
        auto binom(int i, int j) const {
            assert(0 <= i);
            if (j < 0 ||i < j) return Value(0);
            return fact.at(i) * finv.at(j) * finv.at(i - j);
        }
        auto deal(int i, int j) const
            { return binom(i + j - 1, j - 1); }
};

void debug_impl() { std::cerr << std::endl; }
template <typename Head, typename... Tail>
void debug_impl(Head head, Tail... tail) { std::cerr << " " << head; debug_impl(tail...); }
#define DEBUG 1
#if DEBUG
#define debug(...)\
    do {\
        std::cerr << std::boolalpha << "[" << #__VA_ARGS__ << "]:";\
        debug_impl(__VA_ARGS__);\
        std::cerr << std::noboolalpha;\
    } while (false)
#else
#define debug(...) {}
#endif

int main(){
    std::cin.tie(nullptr);std::cin.sync_with_stdio(false);
    int n,k;std::cin>>n>>k;
    factorials<mint>fact;
    fact.build(2*n+1);
    if(n<k){
        std::cout<<fact.deal(n,n)<<std::endl;
    }else{
        mint ans=0;
        for(int i=0;i<=k;i++){
            mint now=fact.binom(n,i)*fact.deal(i,n-i);
            ans+=now;
        }
        std::cout<<ans<<std::endl;
    }
}

Measured memory_bytes: 3328