#pragma GCC optimize("O3") //コンパイラ最適化用

#define _GLIBCXX_DEBUG //配列に[]でアクセス時のエラー表示
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;

#define REP(i, n) for (ll i = 0; i < ll(n); i++)
#define REPD(i, n) for (ll i = n - 1; i >= 0; i--)
#define FOR(i, a, b) for (ll i = a; i < ll(b); i++)
#define FORD(i, a, b) for (ll i = a; i > ll(b); i--)
// xにはvectorなどのコンテナ
#define ALL(x) x.begin(), x.end()
#define SIZE(x) ll(x.size()) // sizeをsize_tからllに直しておく

#define INF 1000000000000 // 10^12:極めて大きい値,∞
const int MOD = 1000000007;
#define MAXR 100000 // 10^5:配列の最大のrange(素数列挙などで使用)
//略記
#define Umap unordered_map
#define Uset unordered_set
const unsigned int BIT_FLAG_0 = (1 << 0); // 0000 0000 0000 0001
const unsigned int BIT_FLAG_1 = (1 << 1); // 0000 0000 0000 0010
const unsigned int BIT_FLAG_2 = (1 << 2); // 0000 0000 0000 0100
const unsigned int BIT_FLAG_3 = (1 << 3); // 0000 0000 0000 1000
const unsigned int BIT_FLAG_4 = (1 << 4); // 0000 0000 0001 0000
const unsigned int BIT_FLAG_5 = (1 << 5); // 0000 0000 0010 0000
const unsigned int BIT_FLAG_6 = (1 << 6); // 0000 0000 0100 0000
const unsigned int BIT_FLAG_7 = (1 << 7); // 0000 0000 1000 0000

void add(long long &a, long long b) {
    a += b;
    if (a >= MOD)
        a -= MOD;
}
template <class T> inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T> inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

// modint: mod 計算を int を扱うように扱える構造体
// https://github.com/drken1215/algorithm/blob/master/MathCombinatorics/mod.cpp
// https://qiita.com/drken/items/3b4fdf0a78e7a138cd9a

template <int MOD> struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0)
            val += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
    constexpr Fp operator+(const Fp &r) const noexcept {
        return Fp(*this) += r;
    }
    constexpr Fp operator-(const Fp &r) const noexcept {
        return Fp(*this) -= r;
    }
    constexpr Fp operator*(const Fp &r) const noexcept {
        return Fp(*this) *= r;
    }
    constexpr Fp operator/(const Fp &r) const noexcept {
        return Fp(*this) /= r;
    }
    constexpr Fp &operator+=(const Fp &r) noexcept {
        val += r.val;
        if (val >= MOD)
            val -= MOD;
        return *this;
    }
    constexpr Fp &operator-=(const Fp &r) noexcept {
        val -= r.val;
        if (val < 0)
            val += MOD;
        return *this;
    }
    constexpr Fp &operator*=(const Fp &r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp &operator/=(const Fp &r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0)
            val += MOD;
        return *this;
    }
    constexpr bool operator==(const Fp &r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator!=(const Fp &r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr ostream &operator<<(ostream &os,
                                         const Fp<MOD> &x) noexcept {
        return os << x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0)
            return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1)
            t = t * a;
        return t;
    }
};

// 二項係数ライブラリ
template <class T> struct BiCoef {
    vector<T> fact_, inv_, finv_;
    constexpr BiCoef() {}
    constexpr BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) {
        init(n);
    }
    constexpr void init(int n) noexcept {
        fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1);
        int MOD = fact_[0].getmod();
        for (int i = 2; i < n; i++) {
            fact_[i] = fact_[i - 1] * i;
            inv_[i] = -inv_[MOD % i] * (MOD / i);
            finv_[i] = finv_[i - 1] * inv_[i];
        }
    }
    constexpr T com(int n, int k) const noexcept {
        if (n < k || n < 0 || k < 0)
            return 0;
        return fact_[n] * finv_[k] * finv_[n - k];
    }
    constexpr T fact(int n) const noexcept {
        if (n < 0)
            return 0;
        return fact_[n];
    }
    // 追加
    constexpr T perm(int n, int k) const noexcept {
        if (n < k || n < 0 || k < 0)
            return 0;
        return fact_[n] * finv_[k] * finv_[n - k] * fact_[k];
    }

    constexpr T inv(int n) const noexcept {
        if (n < 0)
            return 0;
        return inv_[n];
    }
    constexpr T finv(int n) const noexcept {
        if (n < 0)
            return 0;
        return finv_[n];
    }
};

using mint = Fp<MOD>;
BiCoef<mint> bc;
/*
int main() {
    long long N, M, K; cin >> N >> M >> K;
    bc.init(510000); // 忘れない！
    mint sum = 0;
    for (int i = 0; i <= N-1; ++i) {
        for (int j = 0; j <= M-1; ++j) {
            mint tmp = mint(N - i) * mint(M - j) * mint(i + j);
            modpow(mint(i),N); // 引数はllあるいはmintにして渡す
            if (i != 0 && j != 0) tmp *= 2;
            sum += tmp;
        }
    }
    cout << sum * bc.com(N*M-2, K-2) << endl;
}
*/
int main() {

    int n, k;
    cin >> n >> k;
    bc.init(510000);
    mint ans;
    REP(i, k + 1) {
        mint add = bc.com(n, i) * bc.com(n - 1, i);
        ans += add;
    }
    cout << ans << endl;
}


Measured memory_bytes: 15096