I use Dynamic Programming..and i made several tests myself, my code could calculate the right answer = =...sorry for my poor English

Simple tests:

1)
5 2
2 2
?????
ans:XX.XX

2)
4 2
2 2
????
ans:Impossible

3)
15 3
2 1 2
??X?.?.......X?
ans:.?X?.X.......XX

4)
15 5
2 1 2 1 2
??X?.?.X.?.?.X?
ans:Impossible

5)
5 0

XXXXX
ans:Impossible

6)
5 3
1 1 1
X.X.X
ans:X.X.X

7)
5 2
1 1
.?.?.
ans:.X.X.

8)
18 5
3 1 1 3 1
.???.X?.??..?XX?.?
ans:.XXX.X..??..?XX?.X