//imperative
let sumSqr n =
    let mutable res = 0
    for i in 1..n do
        res <- res + i*i
    res

let x = System.Console.ReadLine()|> System.Int32.Parse

sumSqr 10
//common
let rec sumSqrF n =
    if n = 1 then 1
             else n*n + sumSqrF (n - 1)
sumSqr 10
// List comprehension
let sumSqrG n =
    [ for i in 1..n -> i*i] |> List.sum

sumSqrG 10
[ for i in 1..10 do yield i*i; yield i*i*i ]
//Point-Free                      // a' -> (a' -> b') -> 'b
let (>>) f g = (fun x -> g (f x)) // let (|>) x f = f x  let (<|) f x = f x (very usefull)

let sumSqrPF =
    List.map (fun x -> x * x)
    >> List.filter (fun x -> x % 2 = 0)
    >> List.sum

sumSqrPF [1..10]

let flip f x y = f y x

let even = (flip (%) 2) >> ( (=) 0) // чётность\
let sqr x = x * x


let sumSqrPFn n =
    [1..n]
    |> List.map sqr
    |> List.filter even
    |> List.sum

sumSqrPFn 10

let add x y = x + y