overflow x y
  | 10^80 > (read x + read y) = show (read x + read y)
  | otherwise = "overflow"

oF xs'@(x:y:xs)
  | xs == [] = []
  | otherwise  = (overflow x y) : oF xs

main = getContents >>=
         mapM_ putStrLn . oF . filter (/="") . tail . lines