import Data.List (sort, group)

main :: IO ()
main = interact $ show . solve . map read . tail . words

solve :: [Int] -> Int
solve xs = item2pair + item4pair
    where
        item2pair = sum ys
        item4pair = (sum zs) `div` 4
        ys = map (flip div 2) $ filter (>= 2) $ map length $ group $ sort xs
        zs = map (flip mod 2) $ map length $ group $ sort xs