let solve (n: int) (aArr: int array) =
    let aArr' = Array.sortDescending aArr
    let ans =
        aArr'
        |> Array.pairwise
        |> Array.filter (fun (a1, a2) -> a1 <> a2 + 1)
        |> Array.sumBy (fun (a1, a2) -> a1)
    ans + aArr'.[n - 1]

let () =
    let n = stdin.ReadLine() |> int
    let aArr = stdin.ReadLine().Split() |> Array.map int

    solve n aArr |> printfn "%d"