import qualified Data.Text as T
import qualified Data.Text.IO as TI
import Control.Applicative hiding (empty)
import Data.List hiding (concat)
import Data.Map hiding (filter)
import Data.Foldable
import Data.Monoid
import Prelude hiding (concat)
readLines = sequence.flip replicate TI.getLine

readInt::String->Int
readInt=read

count_dict :: (Ord k, Num a) => [k] -> Map k a
count_dict [] = empty
count_dict (x:xs) = 
  let s = count_dict xs in
      insertWithKey (\k x y ->x+y)  x 1 s

main = do
	m <- readInt<$>getLine
	list <- elems.count_dict.concat<$>fmap (fmap (readInt.T.unpack).T.split(==' '))<$>readLines m
	let same=getSum$foldMap (\x->Sum$x`div`2) list
	let not_same=length$filter ((/=0).(`mod`2)) list
	putStrLn$show$not_same`div`4+same