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()))
a0 = [0] * (n//2+1)
a1 = [0] * (n//2+1)
for i in range(n//2):
    a0[i+1] = a0[i] + a[i*2]
if n% 2 != 0:
    a0.append(a0[-1] + a[-1])

max_even = [0] * (n//2+1)
for i in range(n//2):
    max_even[i+1] = max(max_even[i]+a[2*i+1], a0[i+1])

ans = -1e9*n
if n%2 == 0:
    ans = max_even[-1]
else:
    for i in range(0,n//2+1):
        ans = max(ans, max_even[i] + a0[-1] - a0[i+1])
print(ans)