import sys
input = sys.stdin.readline
 
N = int(input())
A = list(map(int, input().split()))
 
Q = [0] * (N+1)
R = [0] * (N+1)
 
for i in range(1, N+1):
    if i % 2 == 1:  # 홀수
        Q[i] = Q[i-1] + A[i-1]
        R[i] = R[i-1] - A[i-1]
    else:           # 짝수
        Q[i] = Q[i-1] - A[i-1]
        R[i] = R[i-1] + A[i-1]
 
ans = -10**30
 
# Q: l 홀수 => l-1 짝수 prefix
min_even_Q = Q[0]  # j=0 (짝수)
for i in range(1, N+1):
    ans = max(ans, Q[i] - min_even_Q)
    if i % 2 == 0:  # j 짝수만
        min_even_Q = min(min_even_Q, Q[i])
 
# R: l 짝수 => l-1 홀수 prefix
INF = 10**30
min_odd_R = INF
for i in range(1, N+1):
    if i % 2 == 1:  # j 홀수면 후보
        min_odd_R = min(min_odd_R, R[i])
    ans = max(ans, R[i] - min_odd_R)
 
print(ans)

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

NQotMSAyIC00IC0yIDM=

5
-1 2 -4 -2 3