import Control.Applicative ((<$>))
import Control.Monad (replicateM)
import Data.List.Split (splitOn)

main :: IO ()
main = do
  n <- getl read
  solve <$> replicateM n (getl words) >>= print

solve :: [[String]] -> Int
solve = sum . map f
  where
    toMinutes = (\[h, m] -> h * 60 + m) . map read . splitOn ":"
    f [s1, s2] = (toMinutes s2 - toMinutes s1) `mod` 1440

getl :: (String -> a) -> IO a
getl f = f <$> getLine