import sys
input = sys.stdin.readline
 
N = int(input())
A = list(map(int, input().split()))
 
bestB = -10**30
bestC = -10**30
curB = 0
curC = 0
 
for i, a in enumerate(A, start=1):
    # 변환 1: 홀수 +, 짝수 -
    Bi = a if i % 2 == 1 else -a
    curB = max(Bi, curB + Bi)
    bestB = max(bestB, curB)
 
    # 변환 2: 홀수 -, 짝수 +
    Ci = -a if i % 2 == 1 else a
    curC = max(Ci, curC + Ci)
    bestC = max(bestC, curC)
 
print(max(bestB, bestC))

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NQotMSAyIC00IC0yIDM=

5
-1 2 -4 -2 3