Given is an integer sequence A_1, ..., A_N of length N.

We will choose exactly \left\lfloor \frac{N}{2} \right\rfloor elements from this sequence so that no two adjacent elements are chosen.

Find the maximum possible sum of the chosen elements.

Here \lfloor x \rfloor denotes the greatest integer not greater than x.

Constraints

* 2 \leq N \leq 2\times 10^5
* |A_i|\leq 10^9
* All values in input are integers.

Input

Input is given from Standard Input in the following format:


N
A_1 ... A_N


Output

Print the maximum possible sum of the chosen elements.

Examples

Input

6
1 2 3 4 5 6


Output

12


Input

5
-1000 -100 -10 0 10


Output

0


Input

10
1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000 1000000000


Output

5000000000


Input

27
18 -28 18 28 -45 90 -45 23 -53 60 28 -74 -71 35 -26 -62 49 -77 57 24 -70 -93 69 -99 59 57 -49


Output

295
N = int(input())
a = list(map(int, input().split()))

C = [0 for _ in range(N)] #奇数個、余裕あり
D = [0 for _ in range(N)] #偶数個
E = [0 for _ in range(N)] #奇数個、余裕なし

E[0] = a[0]

for i in range(1,N):
  if i % 2 == 0:#奇数個
    C[i] = max(C[i-2]+a[i],D[i-1])
    E[i] = E[i-2] + a[i]
  else:
    D[i] = max(D[i-2]+a[i],E[i-1])

if N % 2 == 0:
  print(D[N-1])
else:
  print(C[N-1])
  
#print(C)
#print(D)
#print(E)
    

