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

ans = 0
odd = [0]
odd_r = [0]
sa = 0
for i in range(N):
    odd.append(odd[-1] + A[i*2])
    odd_r.append(odd_r[-1] + A[2*N-1-(i*2)])
    sa += A[2*i] + A[2*i+1]
odd_r.reverse()

ans = abs(odd[-1]-sa+odd[-1])
for i in range(N):
    a = odd[i+1] + odd_r[i+1]
    b = odd_r[i] + odd[i]    
    ans = max(ans, a-sa+a, b-sa+b)
print(ans)