let ``No.45 回転寿司``() =
    
  let n = stdin.ReadLine() |> int
  let v = stdin.ReadLine().Split(' ')
          |> Array.map (fun s -> s |> int)
          |> Array.toList
  let rec loop r l =
    let prepre, pre = r
    match l with
    | []   -> 0
    | [x]  -> max (prepre + x) pre
    | x::xs-> loop (pre, max (prepre + x) pre) xs
  
  loop (0,0) v
  |> stdout.WriteLine

``No.45 回転寿司``()