let N=stdin.ReadLine() |> int
let A=stdin.ReadLine().Split() |> Array.map int
let B=stdin.ReadLine().Split() |> Array.map int
let C=stdin.ReadLine().Split() |> Array.map int

let harmonized before now =
    if now = before + 1 then true
    else false

let eat (before, now) =
    if harmonized before now then
        B.[now-1]+C.[before-1]
    else
        B.[now-1]

let eat2 now = 
    B.[now-1]
 
(
    A 
    |> Array.pairwise
    |> Array.map eat  
    |> Array.sum 
)  
+ eat2 A.[0]
|> stdout.WriteLine