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

main = readLn >>= print . g 3 . f 2 where
    f k x
        | mod x k > 0 = x
        | otherwise   = f k (div x k)
    g i x
        | x < k = x
        | otherwise = g (i + 2) (f k x)
        where k = i * i