factors :: Int -> [Int]
factors n = [x | x <- [1..n], n `mod` x == 0]

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

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