{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE OverloadedLists #-}

module Main where

import qualified Data.Text as T
import qualified Data.Text.IO as T
import Data.List
import Control.Applicative
import Control.Monad
import Data.Char

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

solve :: Int -> Int -> Int -> Int
solve a b c = (\(_, _, _, res) -> res)
  . thirdProcess
  . secondProcess
  . firstProcess $ sorted (a, b, c, 0) where
  sorted :: (Int, Int, Int, Int) -> (Int, Int, Int, Int)
  sorted (a', b', c', res) = (\[a'', b'', c''] -> (a'', b'', c'', res)) $ sub a' b' c' where
    sub :: Int -> Int -> Int -> [Int]
    sub a''' b''' c''' = sort [a''', b''', c''']
  firstProcess :: (Int, Int, Int, Int) -> (Int, Int, Int, Int)
  firstProcess (a', b', c', res)
    | b' == c'              = (a', b', c', res)
    | otherwise             = firstProcess (a' + 1, b' + 1, c', res + 1)
  secondProcess :: (Int, Int, Int, Int) -> (Int, Int, Int, Int) 
  secondProcess (a', b', c', res)
    | a' >= b'              = (a', b', c', res)
    | otherwise             = secondProcess (a' + 2, b', c', res + 1)
  thirdProcess :: (Int, Int, Int, Int) -> (Int, Int, Int, Int)
  thirdProcess (a', b', c', res)
    | a' == b'              = (a', b', c', res)
    | otherwise             = (a', b' + 1, c' + 1, res + 1)