Problem:
Problem Statement

We have N pieces of ropes, numbered 1 through N. The length of piece i is a_i.

At first, for each i (1≤i≤N-1), piece i and piece i+1 are tied at the ends, forming one long rope with N-1 knots. Snuke will try to untie all of the knots by performing the following operation repeatedly:

Choose a (connected) rope with a total length of at least L, then untie one of its knots.

Is it possible to untie all of the N-1 knots by properly applying this operation? If the answer is positive, find one possible order to untie the knots.

Constraints

2≤N≤10^5

1≤L≤10^9

1≤a_i≤10^9

All input values are integers.

Input

The input is given from Standard Input in the following format:

N L
a_1 a_2 ... a_n

Output

If it is not possible to untie all of the N-1 knots, print Impossible.

If it is possible to untie all of the knots, print Possible, then print another N-1 lines that describe a possible order to untie the knots. The j-th of those N-1 lines should contain the index of the knot that is untied in the j-th operation. Here, the index of the knot connecting piece i and piece i+1 is i.

If there is more than one solution, output any.

Sample Input 1

3 50
30 20 10

Sample Output 1

Possible
2
1

If the knot 1 is untied first, the knot 2 will become impossible to untie.

Sample Input 2

2 21
10 10

Sample Output 2

Impossible

Sample Input 3

5 50
10 20 30 40 50

Sample Output 3

Possible
1
2
3
4

Another example of a possible solution is 3, 4, 1, 2.

Solution in OCaml (4.02.3) (judge verdict: Accepted)

let n, l = Scanf.scanf "%d %d\n" (fun x y -> x, y)

let rec read_ints acc = function
  | 0 -> List.rev acc
  | k -> read_ints (Scanf.scanf "%d " (fun x -> x) :: acc) (k-1)

let al = read_ints [] n

let rec solve i k = function
  | [] | _ :: [] -> Some ([], [])
  | hd0 :: ((hd1 :: tl1) as tl0) -> if k < l then None else
    if hd0 + hd1 >= l then
      match solve (i+1) k (hd0 + hd1 :: tl1) with
        | None -> None
        | Some (x, y) -> Some (x, (i :: y))
    else
      match solve (i+1) (k-hd0) tl0 with
        | None -> None
        | Some (x, y) -> Some ((i :: x), y)

let sum = List.fold_left (+) 0 al

let () =
  match solve 1 sum al with
  | None -> print_endline "Impossible"
  | Some (x, y) -> print_endline "Possible"; let p = List.iter (fun x -> print_int x; print_newline ()) in p x; p (List.rev y)