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

#define watch(x) cerr << (#x) << ": " << (x) << endl
#define int long long

const int N = 200009, MOD = 1000000007;
int n, k;

struct mint {
    int val;
 
    mint(int v = 0) {
        val = v % MOD;
        if(val < 0) val += MOD;
    }
 
    static int mod_inv(int a, int m = MOD) {
        int g = m, r = a, x = 0, y = 1;
 
        while (r != 0) {
            int q = g / r;
            g %= r; swap(g, r);
            x -= q * y; swap(x, y);
        }
 
        return x < 0 ? x + m : x;
    }
 
    explicit operator int() const {
        return val;
    }
 
    mint& operator+=(const mint &other) {
        val += other.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
 
    mint& operator-=(const mint &other) {
        val -= other.val;
        if (val < 0) val += MOD;
        return *this;
    }
 
    static unsigned fast_mod(uint64_t x, unsigned m = MOD) {
        return x % m;
    }
 
    mint& operator*=(const mint &other) {
        val = fast_mod((uint64_t) val * other.val);
        return *this;
    }
 
    mint& operator/=(const mint &other) {
        return *this *= other.inv();
    }
 
    friend mint operator+(const mint &a, const mint &b) { return mint(a) += b; }
    friend mint operator-(const mint &a, const mint &b) { return mint(a) -= b; }
    friend mint operator*(const mint &a, const mint &b) { return mint(a) *= b; }
    friend mint operator/(const mint &a, const mint &b) { return mint(a) /= b; }
 
    mint& operator++() {
        val = val == MOD - 1 ? 0 : val + 1;
        return *this;
    }
 
    mint& operator--() {
        val = val == 0 ? MOD - 1 : val - 1;
        return *this;
    }
 
    mint operator++(int32_t) { mint before = *this; ++*this; return before; }
    mint operator--(int32_t) { mint before = *this; --*this; return before; }
 
    mint operator-() const {
        return val == 0 ? 0 : MOD - val;
    }
 
    bool operator==(const mint &other) const { return val == other.val; }
    bool operator!=(const mint &other) const { return val != other.val; }
 
    mint inv() const {
        return mod_inv(val);
    }
 
    mint pow(int p) const {
        assert(p >= 0);
        mint a = *this, result = 1;
 
        while (p > 0) {
            if (p & 1)
                result *= a;
 
            a *= a;
            p >>= 1;
        }
 
        return result;
    }
 
    friend ostream& operator<<(ostream &stream, const mint &m) {
        return stream << m.val;
    }
};

mint f[2*N];
int sz = 1;
mint fac(int i) {
    while(sz <= i) {
        f[sz] = f[sz-1]*sz;
        sz++;
    }
    return f[i];
}
                                                
mint choose(int a, int b) {
    mint num = fac(a);
    mint denom = fac(b)*fac(a-b);
    mint ans = num/denom;
    return ans;
}

int32_t main() {

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> n >> k;
    mint m(n);
    f[0] = 1;
    
    mint bad = 0;
    for(int empty = k+1; empty < n; ++empty) {
        //how many combs are there with `empty` empty rooms?
        mint choice = choose(n, empty);
        mint other = choose(n-1, n-empty-1);
        bad += choice*other;
    }

    mint total = choose(n + n - 1, n);
    mint ans = total - bad;

    cout << ans << '\n';
    
    return 0;
}


Measured memory_bytes: 3328