[<EntryPoint>]
let main argv =
    //printfn "Make it!"
    let n = System.Console.ReadLine() |> int
    let b = System.Console.ReadLine().Split() |> Array.map int
    let ans =
        (List.sumBy (fun i -> if b.[i-1] < b.[i] then b.[i-1] else b.[i]) [1 .. n-2])
        |> (+) (b.[0] + b.[n-2])
    printfn "%d" ans
    0
