import Control.Applicative ((<$>))
import Control.Monad (replicateM)
import Data.Bits (xor)

import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B

import Data.Char (isSpace)

import Data.IntSet (IntSet)
import qualified Data.IntSet as ISet

import Data.List (foldl', unfoldr, nub)


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]] -> Int
solve w h n xss = xs * h + ys * w - xs * ys - n
    where
        xs = length $ nub $ map head xss
        ys = length $ nub $ map (head.tail) xss