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

sum_left = [0] * (n + 1)
for i in range(1, n + 1):
    idx = 2 * (i - 1)
    sum_left[i] = sum_left[i-1] + (a[idx] - a[idx + 1] if idx + 1 < len(a) else 0)

sum_right = [0] * (n + 1)
for i in range(1, n + 1):
    l = 2 * n - 1 - 2 * (i - 1)
    r = l - 1
    if r >= 0:
        sum_right[i] = sum_right[i-1] + (a[l] - a[r])
    else:
        sum_right[i] = sum_right[i-1]

max_diff = -float('inf')
for i in range(n + 1):
    current = sum_left[i] + sum_right[n - i]
    if current > max_diff:
        max_diff = current

print(max_diff)