import java.io._
import java.util.StringTokenizer
import scala.util.control.Breaks.{breakable,break}
import scala.collection.mutable.{Map, Stack, Queue, PriorityQueue, Set}

object Main extends App {
  val in = new InputReader(System.in)
  val pw = new PrintWriter(System.out)

  val MOD = 1e9.toInt + 7

  val n, k = in.next().toInt

  val mc = new ModComb(n, MOD)
  var ans = 0L

  for (i <- 1 to (k min (n-1))) {

    val ball = i
    val stick = (n-i)-1
    ans += mc.comb(n, i) * mc.comb(ball+stick, stick)
    ans %= MOD
  }

  if (k % 2 == 0 || k >= 3) {
    ans += 1
  }

  println(ans)
}


class ModComb(maxNum: Int, mod: Long) {

  private def repeatSquares(x: Long, n: Long): Long = {
    if(n == 0)
      1
    else if(n % 2 == 0)
      repeatSquares(x*x % mod, n/2)
    else
      (x * repeatSquares(x*x % mod, n/2)) % mod
  }

  private val fact = new Array[Long](maxNum + 1)

  fact(0) = 1
  for (i <- 1 to maxNum)
    fact(i) = (i * fact(i-1)) % mod

  val factInv = new Array[Long](maxNum + 1)

  factInv(maxNum) = repeatSquares(fact(maxNum), mod-2)
  for (i <- (1 to maxNum).reverse)
    factInv(i-1) = (i * factInv(i)) % mod


  // nCk
  def comb(n: Int, k: Int): Long = {
    val numer = fact(n)
    val denom = (factInv(n-k) * factInv(k)) % mod

    (numer * denom) % mod
  }

}


object Sub {
  def print2DimArray[A](mat: Array[Array[A]]): Unit = {
    mat.foreach(lin => println(lin.deep))
  }
}

class InputReader(stream: InputStream) {
  private[this] val reader = new BufferedReader(new InputStreamReader(stream))
  private[this] var tokenizer: StringTokenizer = new StringTokenizer(reader.readLine())
  def next(): String = {
    while (!tokenizer.hasMoreTokens()) {
      tokenizer = new StringTokenizer(reader.readLine())
    }
    tokenizer.nextToken()
  }
}
