import Data.List (group, sort)

main = do
    [n, x] <- map read . words <$> getLine
    as <- group . sort . map (read :: String -> Int) . words <$> getLine
    print $ solve x $ take (x + 1) $ (++ (repeat 0)) $ f 0 as

f _ [] = []
f i as 
    | (head . head) as == i = (length . head) as : f (i + 1) (tail as)
    | otherwise             = 0 : f (i + 1) as

solve x as = g 0 where
    g i | i == x    = 0
        | otherwise = a1 * a2 + g (i + 1)
        where
            a1 = as !! i
            a2 = as !! (x - i)