[<AutoOpen>]
module Program

open System

let read f = stdin.ReadLine() |> f
let reads f = stdin.ReadLine().Split() |> Array.toList |> List.map f

[<EntryPoint>]
let main _ =
    let [n;l] = reads int
    let ps = List.map (fun i -> l + i - 1) [1..n]
    let q :: qs = List.sortBy abs ps
    printfn "%i" (List.sum qs)
    0