factors :: Int ->Int -> [Int]
factors n hafN = [x | x <- [1..n], if hafN >= x then n `mod` x == 0 else False ]

sumOfSequences :: Int -> Int
sumOfSequences cnt | cnt <= 0 = 0
                   | otherwise = cnt * ((length $ factors cnt (cnt `div` 2)) + 1) + sumOfSequences (cnt - 1)

main = do
    x <- readLn :: IO Int
    print $ sumOfSequences x