#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAX = 510000;
const int MOD = 1000000007;

ll fac[MAX], finv[MAX], inv[MAX];
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;
    }
}
ll 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;
}

int main(){
    COMinit();
   ll n,k,ans = 0;
   cin >> n >> k;
   for(int i=0;i<=min(n,k);i++) ans = (ans + (COM(n,i)*COM(n-1,i))%MOD)%MOD;
   cout << ans << endl;
}