import strutils, sequtils, algorithm

proc getStr: auto =
  stdin.readLine

proc go(V: seq[int]): int =
  var i = 0
  while i < V.len:
    if i != V.high:
      if V[i] < V[i + 1]:
        inc i
        continue
    inc result, V[i]
    inc i, 2

let
  N = getStr().parseInt
  V = getStr().split.map parseInt

echo max(V.go, V.reversed.go)