import io.StdIn._

object Main extends App {
  val nums = readLine.split(" ").map(_.toLong)
  val N = nums(0)
  val A = nums(1)
  val B = nums(2)

  var prev = 1L
  var result = 0L

  for (i <- 1L until N + 1L) {
    prev = prev * (N - i + 1) / i
    if (i != A && i != B) {
      result += prev
    }
    if (result >= 1000000007L) {
      result = result - 1000000007L
    }
  }

  println(result)
}
