import sys
import pypyjit
import itertools
import heapq
import math
from collections import deque, defaultdict, Counter
import bisect

input = sys.stdin.readline
sys.setrecursionlimit(10 ** 6)
pypyjit.set_param('max_unroll_recursion=-1')


def index_lt(a, x):
    'return largest index s.t. A[i] < x or -1 if it does not exist'
    return bisect.bisect_left(a, x) - 1


def index_le(a, x):
    'return largest index s.t. A[i] <= x or -1 if it does not exist'
    return bisect.bisect_right(a, x) - 1


def index_gt(a, x):
    'return smallest index s.t. A[i] > x or len(a) if it does not exist'
    return bisect.bisect_right(a, x)


def index_ge(a, x):
    'return smallest index s.t. A[i] >= x or len(a) if it does not exist'
    return bisect.bisect_left(a, x)


N = int(input())
A = list(map(int, input().split()))

B = [A[2 * i] - A[2 * i + 1] for i in range(N)]
P = [0] * (N + 1)
for i in range(N):
    P[i + 1] = P[i] + B[i]
Q = [0] * (N + 1)
for i in range(N):
    Q[i + 1] = Q[i] - B[N - 1 - i]
INF = 1 << 50
ans = -INF

for i in range(N + 1):
    ans = max(ans, P[i] + Q[N - i])
print(ans)