Problem:
Score : 100 points

Problem Statement

We have A apples and P pieces of apple.

We can cut an apple into three pieces of apple, and make one apple pie by simmering two pieces of apple in a pan.

Find the maximum number of apple pies we can make with what we have now.

Constraints

All values in input are integers.

0 \leq A, P \leq 100

Input

Input is given from Standard Input in the following format:

A P

Output

Print the maximum number of apple pies we can make with what we have.

Sample Input 1

1 3

Sample Output 1

3

We can first make one apple pie by simmering two of the three pieces of apple. Then, we can make two more by simmering the remaining piece and three more pieces obtained by cutting the whole apple.

Sample Input 2

0 1

Sample Output 2

0

We cannot make an apple pie in this case, unfortunately.

Sample Input 3

32 21

Sample Output 3

58

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

module Main (main) where

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

main :: IO ()
main =
  readInts >>= print . showAnswer . solve

type Input  = [Int]
type Output = Int

solve :: Input -> Output
solve [a,p] = (a*3+p) `div` 2

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
  | ByteString ByteString
  | 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 (ByteString bs) = C8.unpack bs
  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

indexMapBS :: Int -> (Char -> Char) -> ByteString -> ByteString
indexMapBS k f s = C8.concat [s1, C8.singleton (f c), s3]
  where
    (s1, s2) = C8.splitAt (k-1) s
    c = C8.head s2
    s3 = C8.tail s2