-- yukicoder My Practice
-- author: Leonardone @ NEETSDKASU

main = readLn >>= print . f where
    f x = g 3 where
        g i
            | mod x i == 0 = i
            | i * i > x    = if mod x 2 == 0 then div x 2 else x
            | otherwise    = g (i + 1)