{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE RankNTypes #-}
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
import Control.Monad.ST
-- import Debug.Trace
-- trace _ = id

solve :: Int -> [Int] -> Int
solve bN as = cost
  where
  vA = VU.fromListN bN as

  enc (len,i) = len * bN + i
  dec z = divMod z bN
  size = bN*(bN+1)
  (cost, len) = func_from_memo (memovec enc dec size mf [(bN,0)]) (bN,0)
  mf rd (1,i) = return $ (0, vA VU.! i)
  mf rd (len,i) = minimum <$> mapM f [1 .. len-1]
    where f k = do
            (costL, lenL) <- rd (k, i)
            (costR, lenR) <- rd (len-k, i+k)
            return (lenL + lenR + costL + costR, lenL + lenR)

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

tmain :: B.ByteString -> Int
tmain cont =
  let remLines0 = map B.words (B.lines cont)
      [bs_bN]:remLines1 = remLines0
      bN = readBInt bs_bN
      line2:remLines2 = remLines1
      as = map readBInt line2
  in solve bN as

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

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


-------------------------------------------------------------------------------

memovec :: forall a d. (VU.Unbox a, Show a, Show d) =>
           (d -> Int) -> (Int -> d) -> Int -> 
           (forall m. Monad m => (d -> m a) -> d -> m a) ->
           [d] -> (VU.Vector a, VU.Vector Bool, d -> Int)
memovec encode decode size mf ds = (vecV, vecF, encode)
  where
    (vecV, vecF) = mv_enc mf' (map encode ds)

    mf' f' i = mf (f' . encode) (decode i)

    mv_enc :: (forall m. Monad m => (Int -> m a) -> Int -> m a)
           -> [Int] -> (VU.Vector a, VU.Vector Bool)
    mv_enc mf xs = runST $ do
      v      <- VUM.new size
      flags  <- VUM.replicate size False
      forM_ xs $ \x -> calc v flags x
      v'     <- VU.unsafeFreeze v
      flags' <- VU.unsafeFreeze flags
      return (v', flags')

      where

        calc :: forall s. VUM.MVector s a -> VUM.MVector s Bool
                          -> Int -> ST s a
        calc v flags x = VUM.read flags x >>= ite231 (VUM.read v x) else_e
          where
            else_e = do
              val <- mf (calc v flags) x
              VUM.write v x val
              VUM.write flags x True
              return val

func_from_memo :: VU.Unbox a =>
                  (VU.Vector a, VU.Vector Bool, d->Int) -> d -> a
func_from_memo (vecV, vecF, enc) d
  | vecF VU.! x = vecV VU.! x
  | otherwise   = undefined
  where x = enc d

ite231 :: a -> a -> Bool -> a
ite231 then_part else_part cond = if cond then then_part else else_part

-------------------------------------------------------------------------------

inp1 = "4\n10 20 30 40\n"
inp2 = "5\n10 10 10 10 10\n"
inp3 = "3\n1000000000 1000000000 1000000000\n"
inp4 = "6\n7 6 8 6 1 1\n"
tv1 = tmain $ B.pack inp1
tv2 = tmain $ B.pack inp2
tv3 = tmain $ B.pack inp3
tv4 = tmain $ B.pack inp4
test1 = tv1 == 190
test2 = tv2 == 120
test3 = tv3 == 5000000000
test4 = tv4 == 68
alltest = test1 && test2 && test3 && test4

