import Control.Monad
import Data.Maybe
import qualified Data.ByteString.Char8 as BS
import Data.List

readInt = fst . fromJust . BS.readInt
readIntList = map readInt . BS.words
getInt = readInt <$> BS.getLine
getIntList = readIntList <$> BS.getLine

main = do
    [h,w] <- getIntList
    board <- replicateM h getLine
    putStrLn $ if solve 0 board then "Possible" else "Impossible"

solve _ [] = True
solve p (as:ass) | s == [p..smax] = solve smax ass
                 | otherwise = False
    where s = elemIndices '#' as
          smax = maximum s