/*
I am the fire that burns your skin
Soy el fuego que arde tu piel

I am the water that kills your thirst
Soy el agua que mata tu sed

The castle, the tower, I am
El castillo, la torre, yo soy

The sword that keeps the flow
La espada que guarda el caudal

You the air that I breathe
Tú el aire que respiro yo

And the moonlight on the sea
Y la luz de la luna en el mar

The throat that I want to wet
La garganta que ansio mojar

I fear drowning in love
Que temo ahogar de amor

And which desires will you give me?
¿Y cuáles deseos me vas a dar?

You say, 'my treasure just look at it'
Dices tú, 'mi tesoro basta con mirarlo'

And yours will be
Y tuyo será

And yours will be
Y tuyo será
*/
#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;

template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T>
using dijkstra = priority_queue<T, vector<T>, greater<T>>;

typedef long long ll;
typedef unsigned long long ull;
#define fbo find_by_order  // k th index
#define ook order_of_key   // strictly smaller than k
#define PI acos(-1.0)
#define inf 0x3f3f3f3f
#define lead_zero(x) __builtin_clzll(x)
#define trail_zero(x) __builtin_ctzll(x)
#define total_1s(x) __builtin_popcountll(x)
#define first_1(x) __builtin_ffsll(x)
#define log2_(x) __builtin_clz(1) - __builtin_clz(x)
#define isLeap(x) ((x % 400 == 0) || (x % 100 ? x % 4 == 0 : false))
#define QUERY           \
    int test;           \
    scanf("%d", &test); \
    for (int _T = 1; _T <= test; _T++)
#define FAST ios_base::sync_with_stdio(0), cin.tie(0)
#define all(v) v.begin(), v.end()
#define reunique(v) v.resize(std::unique(all(v)) - v.begin())
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pul pair<ull, ull>
#define ff first
#define ss second
#define MERGE(v1, v2, v) merge(all(v1), all(v2), back_inserter(v))
#define MP make_pair
#define EB emplace_back
#define read freopen("input.txt", "r", stdin)
#define write freopen("output.txt", "w", stdout)
#define in_range(v, r, l) upper_bound(all(v), r) - lower_bound(all(v), l)
#define LCM(a, b) (a / __gcd(a, b)) * b;

ll rdn(int y, int m, int d) {
    /* Rata Die day one is 0001-01-01 */
    if (m < 3)
        y--, m += 12;
    return 365 * y + y / 4 - y / 100 + y / 400 + (153 * m - 457) / 5 + d - 306;
}
/* Direction arrays */
/*int dx[] = {1,-1,0,0}, dy[] = {0,0,1,-1};                             */  // 4Direction
/*int dx[] = {1,-1,0,0,1,1,-1,-1}, dy[] = {0,0,1,-1,1,-1,1,-1};         */  // 8Direction
/* int dx[] = {1,-1,1,-1,2,2,-2,-2} , dy[] = {2,2,-2,-2,1,-1,1,-1};     */  // KnightDirection
/* int dx[] = {2,-2,1,1,-1,-1} , dy[] = {0,0,1,-1,1,-1};                */  // HexagonalDirection
/* int day[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; */
mt19937 R(chrono::system_clock().now().time_since_epoch().count());
const int mod = 1e9 + 7;
const int N = 40000005;

ll factorial[N];
ll mod_inv[N];

ll bigmod(ll a, ll e) {
    ll ret = 1;
    while (e) {
        if (e & 1)
            ret *= a, ret %= mod;
        a *= a, a %= mod, e >>= 1;
    }
    return ret;
}

inline ll nCr(int x, int y) {
    return factorial[x] * (mod_inv[y] * mod_inv[x - y] % mod) % mod;
}

int main() {
    factorial[0] = 1;
    for (int i = 1; i < N; ++i)
        factorial[i] = (i * 1LL * factorial[i - 1]) % mod;

    mod_inv[N - 1] = bigmod(factorial[N - 1], mod - 2);
    for (ll i = N - 1; i > 0; --i)
        mod_inv[i - 1] = (i * 1LL * mod_inv[i]) % mod;
    FAST;
    ll n, k;
    cin >> n >> k;
    k = min(n, k);
    ll ans = 0;
    for (int i = 0; i <= k; i++) {
        ans = (ans + (nCr(n, i) * nCr(n-1, i)) % mod) % mod;
    }
    cout << ans << "\n";
}


Measured memory_bytes: 625408