N = 0
dp = []
sushi_list = []

def eat_sushi(index, is_ate):
  if index == N:
    return 0

  if dp[is_ate][index] != -1:
    return dp[is_ate][index]

  if is_ate == 0:
    return max(
      eat_sushi(index+1, 1) + sushi_list[index],
      eat_sushi(index+1, 0)
    )
  else:
    return eat_sushi(index+1, 0)

def main():
  global N
  global dp
  global sushi_list

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

  for is_ate in range(2):
    dp.append([])
    for time in range(N):
      dp[is_ate].append(-1)

  print(max(
    eat_sushi(0, 0),
    eat_sushi(1, 0)
  ))

main()