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):
Bi = a if i % 2 == 1 else -a
Ci = -a if i % 2 == 1 else a
curB = max(Bi, curB + Bi)
bestB = max(bestB, curB)
curC = max(Ci, curC + Ci)
bestC = max(bestC, curC)
print(max(bestB, bestC))
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