import           Control.Monad.State
import           Data.Char
import           Data.Coerce
import           Data.Word
import qualified Data.ByteString                   as BS
import qualified Data.ByteString.Char8             as BSC8
import           Data.IntSet                       (IntSet)
import qualified Data.IntSet                       as IntSet
import qualified Data.Vector.Unboxed               as VU

main :: IO ()
main = do
  w <- readLn :: IO Int
  h <- readLn :: IO Int
  n <- readLn :: IO Int
  (xs, ys) <- VU.unzip . VU.unfoldrN n (runCParser $ (,) <$> int <*> int) <$> BSC8.getContents
  let
    sw = IntSet.fromList $ VU.toList xs
    sh = IntSet.fromList $ VU.toList ys
    ww = IntSet.size sw
    hh = IntSet.size sh
  print $ ww * h + hh * w - ww * hh - n

type CParser a = StateT BSC8.ByteString Maybe a
runCParser :: CParser a -> BSC8.ByteString -> Maybe (a, BSC8.ByteString)
runCParser = runStateT
{-# INLINE runCParser #-}
int :: CParser Int
int = coerce $ BSC8.readInt . BSC8.dropWhile isSpace
{-# INLINE int #-}
int1 :: CParser Int
int1 = fmap (subtract 1) int
{-# INLINE int1 #-}
char :: CParser Char
char = coerce BSC8.uncons
{-# INLINE char #-}
byte :: CParser Word8
byte = coerce BS.uncons
{-# INLINE byte #-}
skipSpaces :: CParser ()
skipSpaces = modify' (BSC8.dropWhile isSpace)
{-# INLINE skipSpaces #-}
seqInput :: Int -> IO (VU.Vector Int)
seqInput n = VU.unfoldrN n (runCParser int) <$> BSC8.getLine
{-# INLINE seqInput #-}
parseN1 :: Int -> IO (VU.Vector Int)
parseN1 n = VU.unfoldrN n (runCParser int) <$> BSC8.getContents
{-# INLINE parseN1 #-}
parseN2 :: Int -> IO (VU.Vector (Int, Int))
parseN2 n = VU.unfoldrN n (runCParser $ (,) <$> int <*> int) <$> BSC8.getContents
{-# INLINE parseN2 #-}
parseN3 :: Int -> IO (VU.Vector (Int, Int, Int))
parseN3 n = VU.unfoldrN n (runCParser $ (,,) <$> int <*> int <*> int) <$> BSC8.getContents
{-# INLINE parseN3 #-}
parseN4 :: Int -> IO (VU.Vector (Int, Int, Int, Int))
parseN4 n = VU.unfoldrN n (runCParser $ (,,,) <$> int <*> int <*> int <*> int) <$> BSC8.getContents
{-# INLINE parseN4 #-}
parseN5 :: Int -> IO (VU.Vector (Int, Int, Int, Int, Int))
parseN5 n = VU.unfoldrN n (runCParser $ (,,,,) <$> int <*> int <*> int <*> int <*> int) <$> BSC8.getContents
{-# INLINE parseN5 #-}
parseANBN :: Int -> IO (VU.Vector Int, VU.Vector Int)
parseANBN n = VU.unzip . VU.unfoldrN n (runCParser $ (,) <$> int <*> int) <$> BSC8.getContents
{-# INLINE parseANBN #-}
parseANBNCN :: Int -> IO (VU.Vector Int, VU.Vector Int, VU.Vector Int)
parseANBNCN n = VU.unzip3 . VU.unfoldrN n (runCParser $ (,,) <$> int <*> int <*> int) <$> BSC8.getContents
{-# INLINE parseANBNCN #-}
type Query5 = (Int, Int, Int, Int, Int)
query5Parser :: CParser Query5
query5Parser = do
  skipSpaces
  t <- char
  case t of
    '0' -> (,,,,) 0 <$> int <*> int <*> int    <*> int
    _   -> (,,,,) 1 <$> int <*> int <*> pure 0 <*> pure 0
parseQ5 :: Int -> IO (VU.Vector Query5)
parseQ5 n = VU.unfoldrN n (runCParser query5Parser) <$> BSC8.getContents
{-# INLINE parseQ5 #-}