main :: IO()
main = getContents >>= putStrLn . show . listToValue . (map readDouble) . words


readDouble :: [Char] -> Int
readDouble = read

hours :: Int -> Int
hours x = x * 3600

minutes :: Int -> Int
minutes x = x * 60

listToValue :: [Int] -> Int
listToValue (x:y:z:_)
  | result < 0 = -1
  | otherwise = result
  where
    result = 1 + (div (hours z) $ (minutes x) - y)