N = int(input())
A = list(map(int, input().split()))
D = []
for i in range(N):
    D.append(A[2 * i] - A[2 * i + 1])

adl = [0]
adr = [0]

for i in range(N):
    adl.append(adl[-1] + D[i])
    adr.append(adr[-1] - D[-i - 1])

adr = adr[::-1]
ans = 0
for i in range(N + 1):
    ans = max(ans, adl[i] + adr[i])

print(ans)