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 = [int(x) for x in input().split()]

dp = [[0]*3]*N

dp[0][0] = 0  # ((i+1)-1)/2
dp[0][1] = 0 # (i+1)/2
dp[0][2] = A[0]  # ((i+1)+1)/2

for i in range(1, N):
    
    if i % 2 == 0:
        dp[i][0] = dp[i-1][0] + A[i]
        dp[i][1] = max(dp[i-1][1], dp[i-1][2])
        dp[i][2] = dp[i-1][2] + A[i]
    else:
        dp[i][0] = max(dp[i-1][0], dp[i-1][1])
        dp[i][1] = dp[i-1][1] + A[i]
        dp[i][2] = dp[i-1][2]

if N % 2 == 0:
    print(max(dp[N-1][1],dp[N-1][2]))
else:
    print(max(dp[N-1][0],dp[N-1][1]))