import sys
input = sys.stdin.readline
 
N = int(input())
A = list(map(int, input().split()))
 
pref0 = [0] * (N+1)
pref1 = [0] * (N+1)
 
for i in range(1, N+1):
    if i % 2 == 1:  # 홀수
        pref0[i] = pref0[i-1] + A[i-1]
        pref1[i] = pref1[i-1] - A[i-1]
    else:           # 짝수
        pref0[i] = pref0[i-1] - A[i-1]
        pref1[i] = pref1[i-1] + A[i-1]
 
ans = -10**30
 
# pref0에서: r 고르고 l-1은 짝수 인덱스여야 함
min_even0 = 0  # pref0[0] (짝수)
for i in range(1, N+1):
    ans = max(ans, pref0[i] - min_even0)
    if i % 2 == 0:
        min_even0 = min(min_even0, pref0[i])
 
# pref1에서: r 고르고 l-1은 짝수 인덱스여야 함
min_even1 = 0  # pref1[0] (짝수)
for i in range(1, N+1):
    ans = max(ans, pref1[i] - min_even1)
    if i % 2 == 0:
        min_even1 = min(min_even1, pref1[i])
 
print(ans)

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

NQotMSAyIC00IC0yIDM=

5
-1 2 -4 -2 3