Problem:
Score : 100 points

Problem Statement

There are N flowers arranged in a row.
For each i (1 \leq i \leq N), the height and the beauty of the i-th flower from the left is h_i and a_i, respectively.
Here, h_1, h_2, \ldots, h_N are all distinct.

Taro is pulling out some flowers so that the following condition is met:

The heights of the remaining flowers are monotonically increasing from left to right.

Find the maximum possible sum of the beauties of the remaining flowers.

Constraints

All values in input are integers.

1 \leq N \leq 2 × 10^5

1 \leq h_i \leq N

h_1, h_2, \ldots, h_N are all distinct.

1 \leq a_i \leq 10^9

Input

Input is given from Standard Input in the following format:

N
h_1 h_2 \ldots h_N
a_1 a_2 \ldots a_N

Output

Print the maximum possible sum of the beauties of the remaining flowers.

Sample Input 1

4
3 1 4 2
10 20 30 40

Sample Output 1

60

We should keep the second and fourth flowers from the left.
Then, the heights would be 1, 2 from left to right, which is monotonically increasing, and the sum of the beauties would be 20 + 40 = 60.

Sample Input 2

1
1
10

Sample Output 2

10

The condition is met already at the beginning.

Sample Input 3

5
1 2 3 4 5
1000000000 1000000000 1000000000 1000000000 1000000000

Sample Output 3

5000000000

The answer may not fit into a 32-bit integer type.

Sample Input 4

9
4 2 5 8 3 6 1 7 9
6 8 8 4 6 3 5 7 5

Sample Output 4

31

We should keep the second, third, sixth, eighth and ninth flowers from the left.

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

-- https://github.com/minoki/my-atcoder-solutions
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE FlexibleContexts #-}
import Data.Char (isSpace)
import Data.Int (Int64)
import Data.List (unfoldr)
import Data.Bifunctor (first)
import Control.Monad
import Control.Monad.ST
import qualified Data.Vector.Unboxed as U
import qualified Data.Vector.Unboxed.Mutable as UM
import qualified Data.ByteString.Char8 as BS
import Data.Bits
import Data.Coerce
import qualified Data.Vector.Generic as G
import qualified Data.Vector.Generic.Mutable as GM
import Control.Monad.Primitive
import Data.Monoid
#ifdef MIN_VERSION_base
#if MIN_VERSION_base(4,9,0)
import Data.Semigroup hiding ((<>),Max(..),Min(..))
#endif
#endif

main = do
  n <- readLn
  hs <- U.unfoldrN n (BS.readInt . BS.dropWhile isSpace) <$> BS.getLine
  as <- U.unfoldrN n (readInt64 . BS.dropWhile isSpace) <$> BS.getLine
  let ht = U.create $ do
        ht <- UM.new n
        flip U.imapM_ hs $ \i h -> do
          UM.write ht (h - 1) i
        return ht
  let (h2i,m) = runST $ do
        h2i <- UM.new n
        let loop !i !j !k | i == n = return k
                          | otherwise = do
                              let j' = ht U.! i
                                  k' = if j < j' then k else k+1
                              UM.write h2i i k'
                              loop (i+1) j' k'
        k <- loop 0 0 0
        h2i <- U.unsafeFreeze h2i
        return (h2i,k+1)
  let result = runST $ do
        tree <- asUnboxedBIT $ new_BIT m
        add_BIT tree 0 (Max 0)
        forM_ [0..n-1] $ \i -> do
          let h = hs U.! i
              k = h2i U.! (h-1)
          Max x <- queryM_BIT tree (k+1)
          add_BIT tree k (Max (x + as U.! i))
        getMax <$> queryM_BIT tree m
  print result

readInt64 :: BS.ByteString -> Maybe (Int64, BS.ByteString)
readInt64 s = first fromIntegral <$> BS.readInt s

--
-- Binary Indexed Tree (BIT)
--

type CommutativeMonoid a = Monoid a

newtype BIT mvec s a = BIT (mvec s a)

-- index: 1-based
-- property: forall vec i. fromVector_BIT vec >>= flip queryM_BIT i == pure (G.scanl (<>) mempty vec G.! i)
queryM_BIT :: (Monoid a, GM.MVector mvec a, PrimMonad m) => BIT mvec (PrimState m) a -> Int -> m a
queryM_BIT (BIT vec) !i = doQuery i mempty
  where
    doQuery 0 !acc = return acc
    doQuery i !acc = do y <- GM.read vec (i - 1)
                        let !j = (i - 1) .&. i
                        doQuery j (y <> acc)

-- index: zero-based
-- property: forall vec i x. do { tree <- fromVector_BIT vec; add_BIT tree i x; return tree } == fromVector_BIT (G.accum (<>) vec [(i,x)])
add_BIT :: (CommutativeMonoid a, GM.MVector mvec a, PrimMonad m) => BIT mvec (PrimState m) a -> Int -> a -> m ()
add_BIT (BIT vec) !i !y = loop (i + 1)
  where
    loop !k | k > GM.length vec = return ()
    loop !k = do x <- GM.read vec (k - 1)
                 GM.write vec (k - 1) $! x <> y
                 loop (k + (k .&. (-k)))

new_BIT :: (Monoid a, GM.MVector mvec a, PrimMonad m) => Int -> m (BIT mvec (PrimState m) a)
new_BIT n = BIT <$> GM.replicate n mempty

asUnboxedBIT :: (PrimMonad m) => m (BIT UM.MVector (PrimState m) a) -> m (BIT UM.MVector (PrimState m) a)
asUnboxedBIT = id

--
-- Max monoid (from Data.Semigroup)
--

newtype Max a = Max { getMax :: a }
#ifdef MIN_VERSION_base
#if MIN_VERSION_base(4,9,0)
instance (Ord a) => Semigroup (Max a) where
  Max x <> Max y = Max (x `max` y)
#endif
#endif
instance (Bounded a, Ord a) => Monoid (Max a) where
  mempty = Max minBound
  Max x `mappend` Max y = Max (x `max` y)

--
-- instance U.Unbox (Max a)
--

newtype instance UM.MVector s (Max a) = MV_Max (UM.MVector s a)
newtype instance U.Vector (Max a) = V_Max (U.Vector a)

instance GM.MVector UM.MVector a => GM.MVector UM.MVector (Max a) where
  basicLength (MV_Max mv) = GM.basicLength mv
  basicUnsafeSlice i l (MV_Max mv) = MV_Max (GM.basicUnsafeSlice i l mv)
  basicOverlaps (MV_Max mv) (MV_Max mv') = GM.basicOverlaps mv mv'
  basicUnsafeNew l = MV_Max <$> GM.basicUnsafeNew l
  basicInitialize (MV_Max mv) = GM.basicInitialize mv
  basicUnsafeReplicate i x = MV_Max <$> GM.basicUnsafeReplicate i (coerce x)
  basicUnsafeRead (MV_Max mv) i = coerce <$> GM.basicUnsafeRead mv i
  basicUnsafeWrite (MV_Max mv) i x = GM.basicUnsafeWrite mv i (coerce x)
  basicClear (MV_Max mv) = GM.basicClear mv
  basicSet (MV_Max mv) x = GM.basicSet mv (coerce x)
  basicUnsafeCopy (MV_Max mv) (MV_Max mv') = GM.basicUnsafeCopy mv mv'
  basicUnsafeMove (MV_Max mv) (MV_Max mv') = GM.basicUnsafeMove mv mv'
  basicUnsafeGrow (MV_Max mv) n = MV_Max <$> GM.basicUnsafeGrow mv n

instance G.Vector U.Vector a => G.Vector U.Vector (Max a) where
  basicUnsafeFreeze (MV_Max mv) = V_Max <$> G.basicUnsafeFreeze mv
  basicUnsafeThaw (V_Max v) = MV_Max <$> G.basicUnsafeThaw v
  basicLength (V_Max v) = G.basicLength v
  basicUnsafeSlice i l (V_Max v) = V_Max (G.basicUnsafeSlice i l v)
  basicUnsafeIndexM (V_Max v) i = coerce <$> G.basicUnsafeIndexM v i
  basicUnsafeCopy (MV_Max mv) (V_Max v) = G.basicUnsafeCopy mv v
  elemseq (V_Max v) x y = G.elemseq v (coerce x) y

instance U.Unbox a => U.Unbox (Max a)