import Data.Char
import Data.Maybe
import Control.Monad
import Control.Monad.ST
import Data.Array.ST
import Data.Array.Unboxed

sieveUA :: Int -> UArray Int Bool
sieveUA top = runSTUArray $ do
    let m = (top-1) `div` 2
        r = floor . sqrt $ fromIntegral top + 1
    sieve <- newArray (1,m) True      -- :: ST s (STUArray s Int Bool)
    forM_ [1..r `div` 2] $ \i -> do
      isPrime <- readArray sieve i
      when isPrime $ do               -- ((2*i+1)^2-1)`div`2 == 2*i*(i+1)
        forM_ [2*i*(i+1), 2*i*(i+2)+1..m] $ \j -> do
          writeArray sieve j False
    return sieve

primesToUA :: Int -> [Int]
primesToUA top = 2 : [i*2+1 | (i,True) <- assocs $ sieveUA top]

main :: IO ()
main = do
  k <- readLn :: IO Int
  n <- readLn :: IO Int
  let ps = dropWhile (<k) $ primesToUA n
  print (func1 [] (map func2 ps))

func1 :: [Int] -> [(Int, Int)] -> Int
func1 acc [] = head acc
func1 acc hps = func1 (func4 acc (func3 [] hps)) (tail hps)

func2 :: Int -> (Int, Int)
func2 p = (until (<10) (sum . map digitToInt . show) p, p) 

func3 :: [(Int, Int)] -> [(Int, Int)] -> [Int]
func3 acc [] = map snd (reverse acc)
func3 acc ((h,p):hps)
  | isJust $ lookup h acc = map snd (reverse acc)
  | otherwise = func3 ((h,p):acc) hps

func4 :: [Int] -> [Int] -> [Int]
func4 hps1 hps2
  | length hps1 > length hps2 = hps1
  | length hps1 < length hps2 = hps2
  | otherwise = max hps1 hps2