import Control.Monad
import qualified Data.Set as S

nub' = S.toList . S.fromList

main = do
 [w,h,n] <- map read <$> replicateM 3 getLine
 sks <- map (map read . words) . lines <$> getContents
 print (match w h n sks)

match :: Integer -> Integer -> Integer -> [[Integer]] -> Integer
match w h n sks = ns*h + nk*w - ns*nk - n
 where
  ns = (fromIntegral . length . nub' . map head) sks
  nk = (fromIntegral . length . nub' . map last) sks