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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;

const int MAX = 1e5 + 5;

int N, L, a[MAX];
vector<int> ans;

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0);
	cin >> N >> L;
	for (int i = 1; i <= N; ++i) cin >> a[i];

	for (int i = 1; i < N; ++i) {
		if (a[i] + a[i + 1] == L) {
			ans.push_back(i);
			for (int j = i - 1; j >= 1; --j) ans.push_back(j);
			for (int j = i + 1; j < N; ++j) ans.push_back(j);

			printf("Possible\n");
			for (int j = (int)ans.size() - 1; j >= 0; --j) {
				printf("%d\n", ans[j]);
			}
			return 0;
		}
	}
	printf("Impossible\n");
}