let rec take count l =
    match count, l with
    | 0, xs -> []
    | n, x::xs -> x::take (n - 1) xs
    | n, [] -> failwith "Index out of range"

let rec skip count l =
    match count, l with
    | 0, xs -> xs
    | n, x::xs -> skip (n - 1) xs
    | n, [] -> failwith "Index out of range"

let rec insert index v l =
    match index, l with
    | 0, xs -> v::xs
    | n, x::xs -> x::insert (n - 1) v xs
    | n, [] -> failwith "Index out of range"

let rec delete index l =
    match index, l with
    | 0, x::xs -> xs
    | n, x::xs -> x::delete (n - 1) xs
    | n, [] -> failwith "Index out of range"