#include<bits/stdc++.h>
using namespace std;
#define inf INT_MAX
#define INF LLONG_MAX
#define ll long long
#define ull unsigned long long
#define M (int)(1e9+7)
#define P pair<int,int>
#define FOR(i,m,n) for(int i=(int)m;i<(int)n;i++)
#define RFOR(i,m,n) for(int i=(int)m;i>=(int)n;i--)
#define rep(i,n) FOR(i,0,n)
#define rrep(i,n) RFOR(i,n,0)
#define all(a) a.begin(),a.end()
const int vx[4] = {0,1,0,-1};
const int vy[4] = {1,0,-1,0};
#define F first
#define S second
#define PB push_back
#define EB emplace_back
#define int ll
#define vi vector<int>
#define IP pair<int,P>
#define PI pair<P,int>
#define PP pair<P,P>
#define Yes(f){cout<<(f?"Yes":"No")<<endl;}
#define YES(f){cout<<(f?"YES":"NO")<<endl;}



struct Mint {
    int x;

    Mint() : x(0) {}

    Mint(int y) : x(y >= 0 ? y % M : (M - (-y) % M) % M) {}

    Mint &operator+=(const Mint &p) {
        if((x += p.x) >= M) x -= M;
        return *this;
    }

    Mint &operator-=(const Mint &p) {
        if((x += M - p.x) >= M) x -= M;
        return *this;
    }

    Mint &operator*=(const Mint &p) {
        x = (int) (1LL * x * p.x % M);
        return *this;
    }

    Mint &operator/=(const Mint &p) {
        *this *= p.inverse();
        return *this;
    }

    Mint operator-() const { return Mint(-x); }

    Mint operator+(const Mint &p) const { return Mint(*this) += p; }

    Mint operator-(const Mint &p) const { return Mint(*this) -= p; }

    Mint operator*(const Mint &p) const { return Mint(*this) *= p; }

    Mint operator/(const Mint &p) const { return Mint(*this) /= p; }

    bool operator==(const Mint &p) const { return x == p.x; }

    bool operator!=(const Mint &p) const { return x != p.x; }

    Mint inverse() const {
        int a = x, b = M, u = 1, v = 0, t;
        while(b > 0) {
            t = a / b;
            swap(a -= t * b, b);
            swap(u -= t * v, v);
        }
        return Mint(u);
    }

    Mint power(int n) const {
        Mint ret(1), mul(x);
        while(n > 0) {
            if(n & 1) ret *= mul;
            mul *= mul;
            n >>= 1;
        }
        return ret;
    }

    friend ostream &operator<<(ostream &os, const Mint &p) {
        return os << p.x;
    }

    friend istream &operator>>(istream &is, Mint &a) {
        int t;
        is >> t;
        a = Mint(t);
        return (is);
    }


};
using mint = Mint;



struct Combinations {
    static int num;
    vi fact,factr,inv;

    Combinations(int num) {

        fact.assign(num+1,0);
        factr.assign(num+1,0);
        inv.assign(num+1,0);
        inv[1]=fact[0]=factr[0]=1;
        FOR(i,2,num+1) inv[i]=inv[M%i]*(M-M/i)%M;
        FOR(i,1,num+1) fact[i]=fact[i-1]*i%M,factr[i]=factr[i-1]*inv[i]%M;
    }


    int comb(int n,int c){
        if(c<0||c>n) return 0;
        return factr[c]*fact[n]%M*factr[n-c]%M;
    }

    int per(int n,int c){
        if(c<0||c>n) return 0;
        return fact[n]*factr[n-c]%M;
    }

    int hcomb(int n,int c){
        if(n==0&&c==0) return 1;
        return comb(n+c-1,c);
    }

};

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout<<fixed<<setprecision(20);

    int n,k;
    cin>>n>>k;
    Combinations comb(n+10);

    Mint ans=0;
    rep(i,min(k,n-1)+1){
        Mint a=comb.comb(n-1,i);
        Mint b=comb.comb(n,n-i);
        ans+=a*b;
    }

    cout<<ans<<endl;


}

Measured memory_bytes: 4992