read H W
read -d "" AA
cnt=0
ans=0

for i1 in `seq $H`
do
	LINE=`echo "${AA}" | sed -n ${i1}p`
	for i2 in `seq $W`
	do
		i2=$((i2 - 1))
		if [ "${LINE:${i2}:1}" = "#" ]
		then
			if [ $((i2 + 1)) -gt ${cnt} ]
			then
				ans=$((ans + 1))
				cnt=$ans
			elif [ $((i2 + 1)) -lt ${cnt} ]
			then
				echo "Impossible"
				exit
			fi
		fi
	done
done
echo "Possible"
