import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	A = getlist()
	Lsum = [0] * N
	Rsum = [0] * N
	Lsum[0] = A[0] - A[1]
	Rsum[-1] = A[-1] - A[-2]
	for i in range(1, N):
		Lsum[i] = Lsum[i - 1] + A[2 * i] - A[2 * i + 1]
		Rsum[-1 - i] = Rsum[-i] + A[-1 - 2 * i] - A[-2 - 2 * i]

	if N == 1:
		print(abs(A[0] - A[1]))
		return

	ans = -INF
	for i in range(N - 1):
		ans = max(ans, Lsum[i] + Rsum[i + 1])

	print(ans)



if __name__ == '__main__':
	main()