import sys
input = sys.stdin.readline
 
N = int(input())
A = list(map(int, input().split()))
 
# 두 가지 prefix
pref0 = 0  # 홀수 시작 패턴
pref1 = 0  # 짝수 시작 패턴
 
min0 = 0
min1 = 0
ans = -10**30
 
for i, a in enumerate(A, start=1):
    if i % 2 == 1:  # 홀수 인덱스
        pref0 += a
        pref1 -= a
    else:           # 짝수 인덱스
        pref0 -= a
        pref1 += a
 
    ans = max(ans, pref0 - min0, pref1 - min1)
    min0 = min(min0, pref0)
    min1 = min(min1, pref1)
 
print(ans)

aW1wb3J0IHN5cwppbnB1dCA9IHN5cy5zdGRpbi5yZWFkbGluZQoKTiA9IGludChpbnB1dCgpKQpBID0gbGlzdChtYXAoaW50LCBpbnB1dCgpLnNwbGl0KCkpKQoKIyDrkZAg6rCA7KeAIHByZWZpeApwcmVmMCA9IDAgICMg7ZmA7IiYIOyLnOyekSDtjKjthLQKcHJlZjEgPSAwICAjIOynneyImCDsi5zsnpEg7Yyo7YS0CgptaW4wID0gMAptaW4xID0gMAphbnMgPSAtMTAqKjMwCgpmb3IgaSwgYSBpbiBlbnVtZXJhdGUoQSwgc3RhcnQ9MSk6CiAgICBpZiBpICUgMiA9PSAxOiAgIyDtmYDsiJgg7J24642x7IqkCiAgICAgICAgcHJlZjAgKz0gYQogICAgICAgIHByZWYxIC09IGEKICAgIGVsc2U6ICAgICAgICAgICAjIOynneyImCDsnbjrjbHsiqQKICAgICAgICBwcmVmMCAtPSBhCiAgICAgICAgcHJlZjEgKz0gYQoKICAgIGFucyA9IG1heChhbnMsIHByZWYwIC0gbWluMCwgcHJlZjEgLSBtaW4xKQogICAgbWluMCA9IG1pbihtaW4wLCBwcmVmMCkKICAgIG1pbjEgPSBtaW4obWluMSwgcHJlZjEpCgpwcmludChhbnMp

NQotMSAyIC00IC0yIDM=

5
-1 2 -4 -2 3