N=int(input())
A=list(map(int,input().split()))

LS=[0]
RS=[0]

for i in range(N):
    LS.append(LS[-1]+A[i*2]-A[i*2+1])

for i in range(N):
    RS.append(RS[-1]+A[-i*2-1]-A[i*2-2])


ANS=-1<<63
for i in range(1,N+1):
    ANS=max(ANS,LS[i]+RS[N-i])

print(ANS)