import Data.Bool (bool)

main :: IO ()
main = do
    [h, w] <- fmap read . words <$> getLine
    xs     <- getContents
    answer $ solve h w xs

type Answer = Bool
answer :: Answer -> IO ()
answer = putStrLn . bool "Impossible" "Possible"

solve :: Int -> Int -> [Char] -> Answer
solve h w = ((h + w - 1) ==) . length . filter ('#' ==)
