Problem:
Score : 400 points

Problem Statement

One day, Niwango-kun, an employee of Dwango Co., Ltd., found an integer sequence (a_1, ..., a_N) of length N.
He is interested in properties of the sequence a.

For a nonempty contiguous subsequence a_l, ..., a_r (1 \leq l \leq r \leq N) of the sequence a, its beauty is defined as a_l + ... + a_r. Niwango-kun wants to know the maximum possible value of the bitwise AND of the beauties of K nonempty contiguous subsequences among all N(N+1)/2 nonempty contiguous subsequences. (Subsequences may share elements.)

Find the maximum possible value for him.

Constraints

2 \leq N \leq 1000

1 \leq a_i \leq 10^9

1 \leq K \leq N(N+1)/2

All numbers given in input are integers

Input

Input is given from Standard Input in the following format:

N K
a_1 a_2 ... a_N

Output

Print the answer.

Sample Input 1

4 2
2 5 2 5

Sample Output 1

12

There are 10 nonempty contiguous subsequences of a. Let us enumerate them:

contiguous subsequences starting from the first element: \{2\}, \{2, 5\}, \{2, 5, 2\}, \{2, 5, 2, 5\}

contiguous subsequences starting from the second element: \{5\}, \{5, 2\}, \{5, 2, 5\}

contiguous subsequences starting from the third element: \{2\}, \{2, 5\}

contiguous subsequences starting from the fourth element: \{5\}

(Note that even if the elements of subsequences are equal, subsequences that have different starting indices are considered to be different.)

The maximum possible bitwise AND of the beauties of two different contiguous subsequences is 12.
This can be achieved by choosing \{5, 2, 5\} (with beauty 12) and \{2, 5, 2, 5\} (with beauty 14).

Sample Input 2

8 4
9 1 8 2 7 5 6 4

Sample Output 2

32

Solution in Haskell (GHC 7.10.3) (judge verdict: Wrong Answer)

{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections #-}
import qualified Data.ByteString.Lazy.Char8 as B
import Data.Maybe
import Data.List
import qualified Data.Vector.Unboxed as VU
import qualified Data.Vector.Unboxed.Mutable as VUM
import Control.Monad

solve :: Int -> Int -> [Int] -> Int
solve n k as = value 0 seq
  where

    size = n * (n+1) `div` 2
    acc = VU.fromList $ scanl' (+) 0 as
    subsum = [(acc VU.! i) - (acc VU.! j) | j <- [0..n], i <- [j+1..n]]
    table = VU.fromList $ concatMap int2bits subsum

    enc k p = (k * 32) + p

    valid0 = replicate size 1

    seq = unfoldr f (valid0, 31)
      where
      f (valid, -1) = Nothing
      f (valid, p) = ans
        where
          nxt = zipWith (*) valid col
          col = [table VU.! (enc k p) | k <- [0..size-1]]
          ans | sum nxt >= k = Just (1, (nxt, p-1))
              | otherwise    = Just (0, (valid, p-1))

    value acc [] = acc
    value acc (b:bs) = value (2*acc + b) bs

int2bits :: Int -> [Int]
int2bits x = take 32 $ unfoldr f x
  where
    f y = Just (q, p)
      where (p,q) = divMod y 2


readBInt :: B.ByteString -> Int
readBInt = fst . fromJust . B.readInt

tmain :: B.ByteString -> Int
tmain cont =
  let remLines0 = map B.words (B.lines cont)
      [bs_n,bs_k]:remLines1 = remLines0
      n = readBInt bs_n
      k = readBInt bs_k
      line2:remLines2 = remLines1
      as = map readBInt line2
  in solve n k as

outAnswer :: Int -> IO ()
outAnswer = putStrLn . show

main :: IO ()
main = outAnswer . tmain =<< B.getContents