Problem:
Score : 100 points

Problem Statement

You are given positive integers A and B.

If A is a divisor of B, print A + B; otherwise, print B - A.

Constraints

All values in input are integers.

1 \leq A \leq B \leq 20

Input

Input is given from Standard Input in the following format:

A B

Output

If A is a divisor of B, print A + B; otherwise, print B - A.

Sample Input 1

4 12

Sample Output 1

16

As 4 is a divisor of 12, 4 + 12 = 16 should be printed.

Sample Input 2

8 20

Sample Output 2

12

Sample Input 3

1 1

Sample Output 3

2

1 is a divisor of 1.

Solution in Haskell (GHC 7.10.3) (judge verdict: Wrong Answer)

module Main (main) where

import qualified Data.ByteString.Char8 as C8
import Data.Bool
import Data.Maybe

main :: IO ()
main = do
  [a,b] <- readInts
  print . showAnswer $ solve (a,b)

type Input  = (Int, Int)
type Output = Int

solve :: Input -> Output
solve (a,b) = if a `mod` b == 0 then a+b else b-a

showAnswer :: Output -> Answer
showAnswer = Number

-- utils
readInts :: IO [Int]
readInts = map (fst . fromJust . C8.readInt) . C8.words <$> C8.getLine

data Answer
  = YesNo Bool
  | YESNO Bool
  | AB Bool
  | Number Int
  | String String
  | Compare Ordering
  | Compare2 Ordering

instance Show Answer where
  show (YesNo b)    = bool "No" "Yes" b
  show (YESNO b)    = bool "NO" "YES" b
  show (AB b)       = bool "B"  "A" b
  show (Number i)   = show i
  show (String s)   = s
  show (Compare o)  = ordering "<" "=" ">" o
  show (Compare2 o) = ordering "Right" "Balanced" "Left" o

ordering :: a -> a -> a -> Ordering -> a
ordering lt eq gt o = case o of
  LT -> lt
  EQ -> eq
  GT -> gt