Problem:
Score : 300 points

Problem Statement

You are given three integers A, B and C. Find the minimum number of operations required to make A, B and C all equal by repeatedly performing the following two kinds of operations in any order:

Choose two among A, B and C, then increase both by 1.

Choose one among A, B and C, then increase it by 2.

It can be proved that we can always make A, B and C all equal by repeatedly performing these operations.

Constraints

0 \leq A,B,C \leq 50

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B C

Output

Print the minimum number of operations required to make A, B and C all equal.

Sample Input 1

2 5 4

Sample Output 1

2

We can make A, B and C all equal by the following operations:

Increase A and C by 1. Now, A, B, C are 3, 5, 5, respectively.

Increase A by 2. Now, A, B, C are 5, 5, 5, respectively.

Sample Input 2

2 6 3

Sample Output 2

5

Sample Input 3

31 41 5

Sample Output 3

23

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

module Main where

main :: IO ()
main = do
  [a, b, c] <- map read . words <$> getLine
  print $ countOperation a b c

countOperation :: Integer -> Integer -> Integer -> Integer
countOperation a b c = foldl count init m 
  where 
    m = format a b c
    max = maximum m
    init = if [a, b, c] /= m then 1 else 0
    count acc y = acc + (max - y) `div` 2


format :: Integer -> Integer -> Integer -> [ Integer ]
format a b c | hoge = xs
                     | poyo = toEven
                     | bazz = toOdd
 where
  xs     = [a, b, c]
  hoge   = length (filter even xs) == 3 || length (filter odd xs) == 3
  poyo   = length (filter odd xs) == 2
  bazz   = length (filter even xs) == 2
  toEven = map fuga xs
  toOdd  = map fizz xs
  fuga x = if odd x then x + 1 else x
  fizz x = if even x then x + 1 else x