program main
  implicit none
  type card
     integer::S,K
  end type card
  integer::W,H,N,i,markmatch,numbermatch
  integer,allocatable::mark(:),number(:)
  type(card),allocatable::cards(:)
  read *,W,H,N
  allocate(mark(W),number(H),cards(N))
  mark   = 0
  number = 0
  read *, cards
  do i=1,N
     mark(cards(i)%S) = 1
     number(cards(i)%K) = 1
  end do
  markmatch = COUNT(mark.eq.1)
  numbermatch = COUNT(number.eq.1)
  print '(i0)',markmatch*H+numbermatch*W-markmatch*numbermatch-N

end program main