Problem:
Twin Prime

Prime numbers are widely applied for cryptographic and communication technology.
A twin prime is a prime number that differs from another prime number by 2.
For example, (5, 7) and (11, 13) are twin prime pairs.

In this problem, we call the greater number of a twin prime "size of the twin prime."

Your task is to create a program which reads an integer n and prints a twin prime which has the maximum size among twin primes less than or equals to n

You may assume that 5 ≤ n ≤ 10000.

Input

The input is a sequence of datasets. The end of the input is indicated by a line containing one zero. Each dataset is formatted as follows:

n (integer)

Output

For each dataset, print the twin prime p and q (p < q). p and q should be separated by a single space.

Sample Input

12
100
200
300
0

Output for the Sample Input

5 7
71 73
197 199
281 283

Solution in Haskell (judge verdict: Accepted)

import Control.Applicative ((<$>))
import Control.Monad (replicateM, unless, when, forM_)
import Data.List (find)

import Data.Vector.Unboxed (Vector, (!))
import qualified Data.Vector.Unboxed as V
import qualified Data.Vector.Unboxed.Mutable as VM

main :: IO ()
main = do
  n <- readLn
  unless (n == 0) $ do
    solve tbl n
    main
  where sz = 10000
        tbl = V.create $ do
          v <- VM.replicate (sz+1) True
          VM.write v 1 False
          forM_ [2 .. sz] $ \i -> do
            p <- VM.read v i
            when p $ do
              forM_ [i*i, i*(i+1) .. sz] $ \j -> do
                VM.write v j False
          return v

solve :: Vector Bool -> Int -> IO ()
solve tbl n = putStrLn . maybe "" (\x -> show (x-2) ++ " " ++ show x) . find f $ [n, n-1 .. 5]
  where f x = tbl ! x && tbl ! (x-2)