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(c) for c in input().split()]
m = 0
t0 = [-1]*n # 最初使える、i以降
t1 = [-1]*n # 使えない
t2 = [-1]*n # 使わないといけない
t0[-1] = a[-1]
t1[-1] = 0
t2[-1] = a[-1]
tmp = 0
for i in range(-1, -n-1, -2):
    tmp += a[i]
    t2[i] = tmp
tmp = 0
for i in range(-2, -n-1, -2):
    tmp += a[i]
    t2[i] = tmp

    
for i in range(-2, -n-1, -1):
    if i%2==0:
        m= a[i]+t1[i+1]
        m = max(m, t2[i+1])
        t0[i] = m
        t1[i] = t0[i+1]
#         t2[i] = a[i] + t1[i+1]
    else:
        m= a[i]+t1[i+1]
        m = max(m, t0[i+1])
        t0[i] = m
        t1[i] = t0[i+1]
#         t2[i] = a[i] + t1[i+1]
        
print(t0[0])