import java.util.Scanner

object Main extends App {
  val sc = new Scanner(System.in)
  val n = sc.nextInt()
  val a = sc.nextInt()
  val b = sc.nextInt()

  val x = (1 to n).filterNot(i => i == a || i == b)

  val max = 200000
  val mod = 1000000007

  val fac = new Array[Long](max)
  val finv = new Array[Long](max)
  val inv = new Array[Long](max)

  def COMInit(): Unit = {
    fac(0) = 1
    fac(1) = 1
    finv(0) = 1
    finv(1) = 1
    inv(1) = 1
    for (i <- 2 until max) {
      fac(i) = fac(i - 1) * i % mod
      inv(i) = mod - inv(mod % i) * (mod / i) % mod
      finv(i) = finv(i - 1) * inv(i) % mod
    }
  }
  COMInit()

  def COM(n: Int, k: Int): Long = {
    if (n < k) 0L
    else if (n < 0 || k < 0) 0L
    else fac(n) * (finv(k) * finv(n - k) % mod) % mod
  }

  val y = x.map(COM(n, _)).sum

  println(y)
}
