import Control.Applicative ((<$>))
import Data.List (find)

main :: IO ()
main = solve <$> read <$> getLine >>= print

solve :: Int -> Int
solve n = maybe m id . find ((== 0) . (mod n)) . takeWhile ((<= n) . (^ 2)) $ [3 ..]
  where m = if even n then n `div` 2 else n