--The answer is written for numbers <= 1000

main :: IO ()
main = putStr $ show $ solve 1000

solve :: Int -> Int
solve n = sum $ map (length . numWord) [1 .. n]

numWord :: Int -> [Char]
numWord n
  | n == 0 = ""
  | n == 1000 = "onethousand"
  | n < 20 = ones !! (n - 1)
  | n < 100 = tens !! (div n 10 - 2) ++ numWord (mod n 10)
  | mod n 100 == 0 = numWord (div n 100) ++ "hundred"
  | otherwise = numWord (div n 100) ++ "hundredand" ++ numWord (mod n 100)
  where
    tens :: [[Char]]
    tens = ["twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]

    ones :: [[Char]]
    ones = ["one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]