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

//repetition
#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i, n) for(ll i = 0; i < (ll)(n); i++)

//container util
#define all(x) (x).begin(),(x).end()

//typedef
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VLL;
typedef vector<VLL> VVLL;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;

//const value
//const ll MOD = 1e9 + 7;
//const int dx[] = {0,1,0,-1};//{0,0,1,1,1,-1,-1,-1};
//const int dy[] = {1,0,-1,0};//{1,-1,0,1,-1,0,1,-1};

//conversion
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
inline ll toLL(string s) {ll v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

template <typename T1, typename T2> 
inline bool chmax(T1 &a, T2 b) {
  return a < b && (a = b, true);
}

template <typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {
  return a > b && (a = b, true);
}
//* Mod int
const int mod = 1000000007;
struct mint {
  ll x;
  mint():x(0){}
  mint(ll x):x((x%mod+mod)%mod){}
  // mint(ll x):x(x){}
  mint& fix() { x = (x%mod+mod)%mod; return *this;}
  mint operator-() const { return mint(0) - *this;}
  mint& operator+=(const mint& a){ if((x+=a.x)>=mod) x-=mod; return *this;}
  mint& operator-=(const mint& a){ if((x+=mod-a.x)>=mod) x-=mod; return *this;}
  mint& operator*=(const mint& a){ (x*=a.x)%=mod; return *this;}
  mint operator+(const mint& a)const{ return mint(*this) += a;}
  mint operator-(const mint& a)const{ return mint(*this) -= a;}
  mint operator*(const mint& a)const{ return mint(*this) *= a;}
  bool operator<(const mint& a)const{ return x < a.x;}
  bool operator==(const mint& a)const{ return x == a.x;}
};
istream& operator>>(istream&i,mint&a){i>>a.x;return i;}
ostream& operator<<(ostream&o,const mint&a){o<<a.x;return o;}
typedef vector<mint> vm;
typedef vector<vm> vvm;
//*/

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

long long fac[MAX];
long long finv[MAX];
long long inv[MAX]; // mod MOD k の逆元 inv[k]

// 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;
}

// 順列計算
long long perm(long long a, long long b){
    if(a < b) return 0;
    long long tmp = finv[a-b] % MOD;
    return tmp * fac[a] % MOD;
}

long long modPow(long long x, long long n){
  if(n == 0) return 1;
  if(n % 2 == 0) {
    long long sqrtX = modPow(x,n/2);
    return sqrtX * sqrtX % MOD ;
  }else{
    return x * modPow(x,n-1) % MOD;
  }
}
// n種類のものから重複を許してr個選ぶ場合の数
ll modH(ll n, ll r){
  return COM(n+r-1,r);
}
int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);
  COMinit();
  ll n,k;
  cin >> n >> k;

  mint ans = 0;
  // 0 の個数
  rep(zeroCnt,min(n,k)+1){
    // n-zeroCntは1個以上必要なので、
    // あらかじめ(n-zeroCnt)個配った中から
    // 重複を許して選ぶ
    ans += COM(n,zeroCnt) * modH(n-zeroCnt,n-(n-zeroCnt));
  }
  cout << ans << endl;
  return 0;
}


Measured memory_bytes: 12160