n = int(input())
a2n = list(map(int, input().split(' ')))

fromL = [None] * n
for i in range(n):
    fromL[i] = a2n[2 * i] - a2n[2 * i + 1]

fromR = [None] * n
a2nd = a2n[::-1]
for i in range(n):
    fromR[i] = a2nd[2 * i] - a2nd[2 * i + 1]

cumL = [None] * (n + 1)
cumL[0] = 0
for i in range(n):
    cumL[i + 1] = cumL[i] + fromL[i]

cumR = [None] * (n + 1)
cumR[0] = 0
for i in range(n):
    cumR[i + 1] = cumR[i] + fromR[i]


results = [None] * (n + 1)
for i in range(n + 1):
   results[i] = cumR[i]+ cumL[n - i]

print(max(results))