import Control.Applicative
import Control.Monad
import Data.List

main :: IO ()
main = do
  getLine
  xs <- f
  if length xs == 3
    then putStrLn "\"assert\""
    else do
      solve (head xs) <$> readLn <*> readLn >>= print
  where
    f = map read <$> words <$> getLine

solve :: Int -> Int -> Int -> Int
solve a b c = let [x, y, z] = sort [a+b, b+c, c+a]
              in if y == z then x else y