object Main extends App {
  val sc = new java.util.Scanner (System.in)
  val n,a,b = sc.nextInt
  def power(x:Int,p:Int):Int = if(p==0) 1 else x * power(x,p-1)
  def prod(x:Int):Int = if (x <= 1) 1 else x * prod(x - 1)
  def comb(n:Int,r:Int):Int= prod(n) / ( prod(n-r) * prod(r) ) 
  val array:Seq[Int] = for ( v <- 2 to n if a != v & b != v) yield comb(n,v)
  println(if (array.isEmpty) 0 else array.foldLeft(0)((a,b)=>a+b)%(power(10,9)+7))
}

