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: Runtime Error)

import Control.Monad

main = do
  li <- getLine
  let [n,m] = map read $ words li
  ass <- forM [1..m] (\_ -> do
    li <- getLine
    let as = map read $ words li
    return (tail as)
   )
  li <- getLine
  let ps = map read $ words li
  let answer = compute n ass ps
  print answer
 
compute n ass ps = length
  [ ()
  | st <- states n
  , and [ isOn bs st p | (bs,p) <- zip bss ps ]
  ]
  where
    bss = map (aij2bs n) ass

states 0 = [ [] ]
states k = let sts = states (pred k)
           in  map (0 :) sts ++ map (1 :) sts

aij2bs n ss = [ elem i ss | i <- [1..n] ]

isOn bs st p = even $ p + sum [ s | (b,s) <- zip bs st, b ]