n = int(input())
a = list(map(int, input().split()))

right = [0]*n
left = [0]*n
nowodd = 0
noweven = 0
for i in range(n):
    if i % 2 == 0:
        noweven = noweven+a[i]
        left[i] = noweven
    if i % 2 == 1:
        nowodd = nowodd+a[i]
        left[i] = nowodd
nowodd = 0
noweven = 0

for i in range(n-1, -1, -1):
    if i % 2 == 0:
        noweven = noweven+a[i]
        right[i] = (noweven)
    if i % 2 == 1:
        nowodd = nowodd+a[i]
        right[i] = (nowodd)
nux = 0
for i in range(n-3):
    if nux < left[i]+right[i+3]:
        nux = left[i]+right[i+3]


print(max(nux, left[n-1], left[n-2]))