import           Control.Monad         ( replicateM )
import           Data.Char             ( isSpace )
import qualified Data.List             as L
import qualified Data.ByteString.Char8 as BSC8

input :: Int -> IO [[Int]]
input n = replicateM n $ my <$> BSC8.getLine
  where
    my :: BSC8.ByteString -> [Int]
    my = L.unfoldr f
      where
        f s = do
          (n, s') <- BSC8.readInt s
          return (n, BSC8.dropWhile isSpace s')

main :: IO ()
main = do
  w <- readLn :: IO Int
  h <- readLn :: IO Int
  n <- readLn :: IO Int
  xss <- input n
  let
    x = L.length $ L.nub $ L.map L.head xss
    y = L.length $ L.nub $ L.map L.last xss
    a = w * h - ((w - x) * (h - y) + n)
  print a