import Data.List

main = readLn >>= print . pairs
pairs n = length . filter (odd . foldl1' subtract) . 
          combination 2 $ [1 .. n] where
combination 0 _         = [[]]
combination _ []        = []
combination n (x : xs)  = map (x :) (combination (n - 1) xs) ++
                          combination n xs 
