#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define db double
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
const int inf = 1 << 30;
const ll linf = 1e18;
template<class T> void chmin(T& x, T y){if(x > y) x = y;}
template<class T> void chmax(T& x, T y){if(x < y) x = y;}

template<long long mod>
struct modint{
    long long num;

    constexpr modint(long long x = 0) : num((x + mod) % mod) {}

    constexpr modint &operator += (const modint& rhs){
        num = (num + rhs.num) % mod;
        return *this;
    }
    constexpr modint &operator -= (const modint& rhs){
        num  -= rhs.num;
        while(num < 0) num += mod;
        num %= mod;
        return *this;
    }
    constexpr modint &operator *= (const modint& rhs){
        num = num * rhs.num % mod;
        return *this;
    }
    constexpr modint &operator /= (modint rhs){
        int exp = mod - 2;
        while(exp > 0){
            if(exp % 2){
                *this *= rhs;
            }
            rhs *= rhs;
            exp /= 2;
        }
        return *this;
    }

    constexpr modint operator ++ (){
        ++num;
        return *this;
    }

    constexpr modint operator ++ (int n){
        modint tmp = *this;
        ++(*this);
        return tmp;
    }

    constexpr modint operator -- (){
        --num;
        return *this;
    }
    constexpr modint operator -- (int n){
        const modint tmp = *this;
        --(*this);
        return tmp;
    }

    void modpow(ll y){
        modint tmp = (*this);
        y--;
        while(y > 0){
            if(y % 2){
                (*this) *= tmp;
            }
            tmp *= tmp;
            y /= 2;
        }

    }


    constexpr modint operator + (const modint& rhs) const {
        return modint(*this) += rhs;
    }
    constexpr modint operator - (const modint& rhs) const {
        return modint(*this) -= rhs;
    }
    constexpr modint operator * (const modint& rhs) const {
        return modint(*this) *= rhs;
    }
    constexpr modint operator / (const modint& rhs) const {
        return modint(*this) /= rhs;
    }

    
    friend ostream &operator << (ostream& lhs, const modint& rhs){
        return lhs << rhs.num;
    }

    friend istream &operator >> (istream& lhs, modint& rhs){
        long long tmp;
        lhs >> rhs.num;
        return lhs;
    }
};

#define mint modint<1000000007>

const ll mod = 1e9 + 7;
ll fac[200010];
ll rec[200010];
ll modpow(ll x, int y){
    if(y == 0) return 1;
    ll e = modpow(x, y / 2);
    e = e * e % mod;
    return e * (y % 2 == 0 ? 1 : x) % mod;
}

void setting(){
    int N = 2e5;
    fac[0] = rec[0] = 1;
    for(int i = 1; i <= N; i++){
        fac[i] = fac[i - 1] * i % mod;
        rec[i] = modpow(fac[i], mod - 2);
    }
}

ll comb(int p, int r){
    ll res = fac[p] * rec[r] % mod;
    res = res * rec[p - r] % mod;
    return res;
}

ll perm(int p, int r){
    ll res = fac[p] * rec[p - r] % mod;
}

int n, k;
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> n >> k;
    setting();
    mint ans(0);
    for(int i = 0; i <= min(k, n - 1); i++){
        ans += comb(n, i) * comb(n - 1, i);
    }
    cout << ans << endl;
    return 0;
}

Measured memory_bytes: 3328