#include <bits/stdc++.h>
using namespace std;

const long long MOD = 1000000007;
const int MAX = 510000;

long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

// 二項係数計算
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

struct GCDResult{long long x; long long y; long long res;};
GCDResult gcd(long long a, long long b){
    if(a < 0){
        auto sub = gcd(-a, b);
        return GCDResult{-sub.x, sub.y, sub.res};
    }
    if(b < 0){
        auto sub = gcd(a, -b);
        return GCDResult{sub.x, -sub.y, sub.res};
    }
    if(a < b){
        auto sub = gcd(b, a);
        return GCDResult{sub.y, sub.x, sub.res};
    }
    // a >= b AND a >= 0 AND b >= 0
    if(b == 0){
        return GCDResult{1LL, 0LL, a};
    }
    // a >= b AND a > 0 AND b > 0
    auto sub = gcd(b, a % b);
    return GCDResult{sub.y, sub.x - sub.y*(a/b), sub.res};
}

template <long long p>
class Zp{
    long long content;
    public:
    Zp(long long content_){
        if(content_ >= 0){
            content = content_ % p;
        }else{
            long long temp = p;
            while(temp < -content_){
                temp *= p;
            }
            content = (temp + content_) % p;
        }
    }

    bool operator==(const Zp<p>& rhs) const{
        return this->content == rhs.content;
    }

    bool operator!=(const Zp<p>& rhs) const{
        return !(*this == rhs);
    }

    Zp<p> operator+(const Zp<p>& rhs) const{
        return Zp<p>(this->content + rhs.content);
    }

    Zp<p> operator-() const{
        return Zp<p>(p - this->content);
    }

    Zp<p> operator-(const Zp<p>& rhs) const{
        return Zp<p>(this->content - rhs.content + p);
    }

    Zp<p> operator*(const Zp<p>& rhs) const{
        return Zp<p>(this->content * rhs.content);
    }

    Zp<p> inv() const{
        if(this->content == 0){
            assert(false);
        }

        auto res = gcd(this->content, p);
        return Zp<p>(res.x);
    }

    Zp<p> operator/(const Zp<p>& rhs) const{
        if(rhs.content == 0){
            assert(false);
        }
        
        return (*this)*rhs.inv();
    }

    Zp<p> pow(int n){
        auto res = Zp<p>(1);
        Zp<p> mult = (*this);
        while(n > 0){
            if(n & 1 == 1){
                res = res*mult;
            }
            n >>= 1;
            mult = mult*mult;
        }
        return res;
    }

    long long raw(){
        return this->content;
    }

};


Zp<MOD> f(long long rooms, long long people){
    return Zp<MOD>(COM(people + rooms - 1, rooms - 1));
}


void solve(long long n, long long k){
    if(n <= k){
        cout << COM(2*n - 1, n - 1) << endl;
    }else{
        // n > k
        auto res = f(n, n);
        for(int i=k+1; i <= n; i++){
            res = res - Zp<MOD>(COM(n, i))*f(n-i, n - (n-i));
        }
        cout << res.raw() << endl;
    }
}

// Generated by 1.1.6 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
int main(){
    COMinit();
    // cout << COM(400000-1, 200000-1) << endl;
    long long n;
    scanf("%lld",&n);
    long long k;
    scanf("%lld",&k);
    solve(n, k);
    return 0;
}


Measured memory_bytes: 12160