There are n boxes. Boxes contain marbles.
Box number 1 contains 1 marble.
Box number 2 contains 2 marbles.
...
Box number n contains n marbles.

We have to choose exactly b boxes out of n original boxes, so that we would have exactly t marbles in total.

For example, if we have a set of boxes B = {1, 2, 3, 4, 5} and we have to choose b = 4 boxes to get the total target value t = 13, then we should output 1 3 4 5.

But if we have the same set of boxes B = {1, 2, 3, 4, 5} and we have to choose b = 3 boxes with the same total value of t = 13, then we have to print Impossible.