import Control.Applicative ((<$>))
import Control.Monad (replicateM)
import Data.List (unfoldr)
import Data.Char (isSpace)
import Data.IntSet (IntSet)
import qualified Data.IntSet as IntSet
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B

getL :: (ByteString -> [Int]) -> IO [Int]
getL f = f <$> B.getLine

readIL :: (ByteString -> Maybe (Int, ByteString)) -> (ByteString -> [Int])
readIL f = unfoldr g
    where
        g s = do
            (n, s') <- f s
            return (n, B.dropWhile isSpace s')

main :: IO ()
main = do
    w <- readLn :: IO Int
    h <- readLn :: IO Int
    n <- readLn :: IO Int
    xss <- replicateM n $ getL (readIL B.readInt)
    print =<< solve w h n xss

solve :: Int -> Int -> Int -> [[Int]] -> IO Int
solve w h n xss = do
    let nxs = IntSet.size $ IntSet.fromList $ map head xss
        nys = IntSet.size $ IntSet.fromList $ map last xss
    return $ w * h  - ((w - nxs) * (h - nys) + n)