import scala.io.StdIn

object Main {
  def main(args: Array[String]): Unit = {
    val w, h, n = StdIn.readInt

    var ss = Set[Int]()
    var ks = Set[Int]()

    for (i <- (0 until n)) {
      val Array(s, k) = StdIn.readLine().split(' ').map(_.toInt)
      ss += s
      ks += k
    }

    val ans = w * h - (w - ss.size) * (h - ks.size) - n
    println(ans)
  }
}