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()))

if N%2==0:
    S = [0]*N
    s = 0
    for i in range(0, N, 2):
        s += A[i]
        S[i] = s

    ans = s = sum(A[1:N:2])
    for t in range(1, N, 2):
        s -= A[t]
        ans = max(ans, S[t-1]+s)
    print(ans)

else:
    S = [0]*N
    s = 0
    p = 0
    for t in range(2, N, 2):
        p += A[t-2]
        S[t] = max(S[t-2]+A[t-1], p)
    
    ans = s = sum(A[2:N:2])
    for t in range(2, N, 2):
        s -= A[t]
        ans = max(ans, S[t]+s)
    print(ans)
    
