module Main where

import           Debug.Trace
import qualified Data.Vector.Unboxed           as VU
import           Data.List
import qualified Data.ByteString               as BS
import qualified Data.ByteString.Char8         as BSC8
import           Data.Char
import           Data.Maybe


getVUIntFromInputLineAtBSC8 :: IO (VU.Vector Int)
getVUIntFromInputLineAtBSC8 =
    VU.unfoldr (BSC8.readInt . BSC8.dropWhile isSpace) <$> BSC8.getLine
getListIntFromInputLineAtBSC8 =
    unfoldr (BSC8.readInt . BSC8.dropWhile isSpace) <$> BSC8.getLine
readInt = fst . fromJust . BSC8.readInt
readIntList = map readInt . BSC8.words
getInt = readInt <$> BS.getLine
getIntList = readIntList <$> BS.getLine

main :: IO ()
main = do
    [aM,aN] <- getListIntFromInputLineAtBSC8
    --aP                   <- getVUIntFromInputLineAtBSC8
    --aQ                   <- getVUIntFromInputLineAtBSC8
    --aR                   <- getVUIntFromInputLineAtBSC8

    --vP <- VU.fromList . take aX . reverse . sort <$> getIntList
    --vQ <- VU.fromList . take aY . reverse . sort <$> getIntList
    --vR <- VU.fromList . take (aX + aY) . reverse . sort <$> getIntList

    let combi = aM*(aM-1) `div` 2 + aN*(aN-1) `div` 2
    print combi

