Problem:
Score : 600 points

Problem Statement

Snuke stands on a number line. He has L ears, and he will walk along the line continuously under the following conditions:

He never visits a point with coordinate less than 0, or a point with coordinate greater than L.

He starts walking at a point with integer coordinate, and also finishes walking at a point with integer coordinate.

He only changes direction at a point with integer coordinate.

Each time when Snuke passes a point with coordinate i-0.5, where i is an integer, he put a stone in his i-th ear.

After Snuke finishes walking, Ringo will repeat the following operations in some order so that, for each i, Snuke's i-th ear contains A_i stones:

Put a stone in one of Snuke's ears.

Remove a stone from one of Snuke's ears.

Find the minimum number of operations required when Ringo can freely decide how Snuke walks.

Constraints

1 \leq L \leq 2\times 10^5

0 \leq A_i \leq 10^9(1\leq i\leq L)

All values in input are integers.

Input

Input is given from Standard Input in the following format:

L
A_1
:
A_L

Output

Print the minimum number of operations required when Ringo can freely decide how Snuke walks.

Sample Input 1

4
1
0
2
3

Sample Output 1

1

Assume that Snuke walks as follows:

He starts walking at coordinate 3 and finishes walking at coordinate 4, visiting coordinates 3,4,3,2,3,4 in this order.

Then, Snuke's four ears will contain 0,0,2,3 stones, respectively.
Ringo can satisfy the requirement by putting one stone in the first ear.

Sample Input 2

8
2
0
0
2
1
3
4
1

Sample Output 2

3

Sample Input 3

7
314159265
358979323
846264338
327950288
419716939
937510582
0

Sample Output 3

1

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

{-# LANGUAGE
  ScopedTypeVariables, BangPatterns, TupleSections, ExplicitForAll,
  LambdaCase, MultiWayIf, Unsafe, RecordWildCards, FlexibleContexts, CPP,
  NoMonomorphismRestriction, GADTs,
  RankNTypes, EmptyDataDecls, EmptyCase, ViewPatterns #-}

import Data.Bits
import Data.List
import qualified Data.ByteString.Char8 as BS
import qualified Data.ByteString.Lazy.Char8 as BSL
import Data.IntMap.Strict (IntMap)
import qualified Data.IntMap.Strict as IMS
import qualified Data.IntMap.Lazy as IML
import Data.IntSet (IntSet)
import qualified Data.IntSet as IS
import qualified Data.Sequence as Seq
import Data.Sequence (Seq)
import qualified Data.Array.IArray as A
import qualified Data.Array.MArray.Safe as A
import qualified Data.Array.MArray as A
import Data.Array (Array)
import Data.Array.Unboxed (UArray)
import Data.Array.IArray (IArray)
import Data.Array.MArray.Safe (MArray)
import Data.Array.IO.Safe (IOArray, IOUArray)
import Data.Array.ST.Safe (STArray, STUArray, runSTArray, runSTUArray)
import qualified Data.Vector as V
import qualified Data.Vector.Unboxed as VU
import qualified Data.Vector.Unboxed.Mutable as VUM
import Control.Monad
import Control.Monad.ST
-- import Control.Monad.ST.Safe
import Control.Applicative
import Data.Maybe
import Data.Tuple
import Data.Ord
import Control.Monad.State.Strict
import Data.Int
import Data.Word
import System.IO
import Data.Function
import Control.Monad.Primitive
import qualified Data.Vector.Primitive.Mutable as VPM
import qualified Data.Vector.Generic.Mutable as VGM
import Data.STRef
import Data.IORef


main :: IO ()
main = do
  n <- readInt <$> getLine
  as <- VU.unfoldrN n (runStateT rInt) <$> BSL.getContents
  print $ (\(l0,lev,od,rev,r0) -> minimum [l0,lev,od,rev,r0]) $
    VU.foldl' (\(!l0,!lev,!od,!rev,!r0) a ->
                 (l0+a,
                  min l0 lev + if | a == 0 -> 2 | even a -> 0 | otherwise -> 1,
                  minimum [l0,lev,od] + if odd a then 0 else 1,
                  minimum [l0,lev,od,rev]
                        + if | a == 0 -> 2 | even a -> 0 | otherwise -> 1,
                  minimum [l0,lev,od,rev,r0] + a)) (0,0,0,0,0) as
  

rInt :: StateT BSL.ByteString Maybe Int
rInt = StateT $ BSL.readInt . BSL.dropWhile (<'!')

#define D(f,r,d) f::Integral a=>a->d;f=fromIntegral;r::String->d;r=read
#define C(f,r,g,h,d) D(f,r,d);g,h::RealFrac a=>a->d;g=floor;h=ceiling
C(_toInteger_,readInteger,floorInteger,ceilInteger,Integer)
C(toInt,readInt,floorInt,ceilInt,Int)
C(toI8,readI8,floorI8,ceilI8,Int8)
C(toI16,readI16,floorI16,ceilI16,Int16)
C(toI32,readI32,floorI32,ceilI32,Int32)
C(toI64,readI64,floorI64,ceilI64,Int64)
C(toWord,readWord,floorWord,ceilWord,Word)
C(toW8,readW8,floorW8,ceilW8,Word8)
C(toW16,readW16,floorW16,ceilW16,Word16)
C(toW32,readW32,floorW32,ceilW32,Word32)
C(toW64,readW64,floorW64,ceilW64,Word64)
D(toDouble,readDouble,Double)
D(toFloat,readFloat,Float)
#undef D
#undef C


#define N(f,g,a,m)\
  f :: forall e i s. (C(a,m)A.Ix i) => (i,i) -> e -> m (a i e); f=A.newArray;\
  g :: forall e i s. (C(a,m)A.Ix i) => (i,i) -> m (a i e); g=A.newArray_
#define C(a,m)
N(newIOA,newIOA_,IOArray,IO)
N(newSTA,newSTA_,STArray s,ST s)
#undef C
#define C(a,m) MArray (a) e (m), 
N(newIOUA,newIOUA_,IOUArray,IO)
N(newSTUA,newSTUA_,STUArray s,ST s)
#undef C
#undef N