Problem:
Score : 200 points

Problem Statement

Find the sum of the integers between 1 and N (inclusive), whose sum of digits written in base 10 is between A and B (inclusive).

Constraints

1 \leq N \leq 10^4

1 \leq A \leq B \leq 36

All input values are integers.

Input

Input is given from Standard Input in the following format:

N A B

Output

Print the sum of the integers between 1 and N (inclusive), whose sum of digits written in base 10 is between A and B (inclusive).

Sample Input 1

20 2 5

Sample Output 1

84

Among the integers not greater than 20, the ones whose sums of digits are between 2 and 5, are: 2,3,4,5,11,12,13,14 and 20. We should print the sum of these, 84.

Sample Input 2

10 1 2

Sample Output 2

13

Sample Input 3

100 4 16

Sample Output 3

4554

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

import Data.List (unfoldr)
import Data.Tuple (swap)

toDigits :: Int -> [Int]
toDigits = unfoldr phi
  where
    phi n = if n /= 0 then Just (swap (n `divMod` 10)) else Nothing

calc :: [Int] -> Int
calc [n,a,b] = sum $ filter p [1..n]
  where
    p m = a <= s && s <= b where s = sum (toDigits m)

main :: IO ()
main = print . calc =<< fmap read . words <$> getLine