import scala.io.StdIn

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

    val sk = (0 until n).map(_ => StdIn.readLine())
    val s_set = sk.map(x => x.split(' ')(0)).toSet
    val k_set = sk.map(x => x.split(' ')(1)).toSet

    val ans = w * h - (w - s_set.size) * (h - k_set.size) - n
    println(ans)
  }
}