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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)


import java.util.Arrays;
import java.util.Scanner;

/*
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/**
 *
 * @author Jiakang Chen
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int N = sc.nextInt();
        
        int L = sc.nextInt();
        Rope[] S = new Rope[N];
        
        for (int i = 0; i < N; i++) {
            S[i] = new Rope(i + 1, sc.nextInt());
        }
        
        int x = isValid(S, L);
        if (x != -1) {
            System.out.println("Possible");
            for (int i = 1; i < x; i++) {
                System.out.println(i);
            }
            
            for (int i = N - 1; i > x; i--) {
                System.out.println(i);
            }
            
            System.out.println(x);
        } else {
            System.out.println("Impossible");
        }
    }
    
    public static int isValid(Rope[] S, int L) {
        for (int i = 0; i < S.length - 1; i++) {
            if (S[i].l + S[i + 1].l >= L) {
                return S[i].i;
            }
        }
        
        return -1;
    }
}

class Rope implements Comparable<Rope> {
    public int i;
    public int l;
    
    public Rope(int index, int length) {
        i = index;
        l = length;
    }
    
    public int compareTo(Rope other) {
        return this.l - other.l;
    }
}