n=int(input())
a=list(map(int,input().split()))
odd=[0]
even=[0]
sum_a=0
for i in range(2*n):
  if i%2==0:
    odd.append(a[i]+odd[-1])
  else:
    even.append(a[i]+even[-1])
  sum_a+=a[i]
ans=0
sum_even=even[-1]
for i in range(n+1):
  score_A=odd[i]+sum_even-even[i]
  ans=max(ans,2*score_A-sum_a)
print(ans)