import Control.Applicative ((<$>))
import Data.List (sort)

main :: IO ()
main = solve <$> map read <$> words <$> getLine >>= print

solve :: [Int] -> Int
solve xs = bsearch (judge (a, b, c)) a c
  where [a, b, c] = sort xs

bsearch :: (Int -> Bool) -> Int -> Int -> Int
bsearch f o n | n - o <= 1 = o
              | f m = bsearch f m n
              | otherwise = bsearch f o m
  where m = (o + n) `div` 2

judge :: (Int, Int, Int) -> Int -> Bool
judge (a, b, c) m = (m > b && 2*m - a - b <= (c - m) `div` 2) ||
                    (m <= b && m - a <= (b - m) `div` 2 + (c - m) `div` 2)