import Control.Applicative
import Control.Monad
import Data.List
import Data.Array.IO
import qualified Data.Vector as V
import qualified Data.Map as M
import Debug.Trace

main = do
  [n, m] <- map read . words <$> getLine
  g <- newArray (0, n - 1) [] :: IO (IOArray Int [Int])
  forM_ [1..m] $ \_ -> do
    [u, v] <- map pred . map read . words <$> getLine
    readArray g u >>= writeArray g u . (v:)
    readArray g v >>= writeArray g v . (u:)
  g' <- V.fromList <$> getElems g
  let (c, f) = testBipartite g'
  let white = length . filter (==True) . map snd . M.toList $ c
  let black = length . filter (==False) . map snd . M.toList $ c
  print $ if f then white*black - m
               else n*(n-1)`div`2 - m

testBipartite :: V.Vector [Int] -> (M.Map Int Bool, Bool)
testBipartite = dfs 0 False M.empty

dfs :: Int -> Bool -> M.Map Int Bool -> V.Vector [Int] -> (M.Map Int Bool, Bool)
dfs u c m g = foldl' f (M.insert u c m, True) $ g V.! u
  where
    f :: (M.Map Int Bool, Bool) -> Int -> (M.Map Int Bool, Bool)
    f (m, False) _ = (m, False)
    f (m, True) v = case M.lookup v m
                    of Just c' -> (m, c /= c')
                       Nothing -> dfs v (not c) m g
