module Main where

import Data.List (sort)

type Input  = [Int]
type Output = Int

parse :: String -> Input
parse =
    map read
    . words
    . (!! 1)
    . lines

solve :: Input -> Output
solve a =
    let
        mulSum xs = f xs
            where
            f (x:y : xs) = x * y + f xs
            f _          = 0
    in
        mulSum . sort $ a

render :: Output -> String
render = show

main :: IO ()
main =
    interact
        ( render
        . solve
        . parse
        )