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 Rust (1.15.1) (judge verdict: Wrong Answer)

use std::io;
use std::io::Read;
use std::collections::VecDeque;

fn main() {
    let mut stdin = io::stdin();
    let mut lines = String::new();
    let _ = stdin.read_to_string(&mut lines);
    let vec = lines.lines().collect::<Vec<&str>>();
    let vec2 = vec[0].split_whitespace().collect::<Vec<&str>>();
    let n :usize = vec2[0].parse().unwrap();
    let l :usize = vec2[1].parse().unwrap();
    let a :Vec<usize> = vec[1].split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut q :VecDeque<usize> = VecDeque::new();
    let mut b :Vec<(usize,usize)> = Vec::new();
    let mut junjo :Vec<usize> = Vec::new();
    for i in 0..(n-1) {
        b.push((1,a[i]));
        q.push_back(i);
    }
    b.push((1,a[n-1]));
    while let Some(i) = q.pop_front() {
        let (honsuu, nagasa) = b[i];
        if i+honsuu >= n {
            println!("Possible");
            while let Some(j) = junjo.pop() {
                println!("{}", j);
            }
            break;
        }
        let (honsuu2, nagasa2) = b[i+honsuu];
        let nagasa3 = nagasa + nagasa2;
        if nagasa3 < l { continue; }
        junjo.push(i+honsuu);
        b[i] = (honsuu+honsuu2, nagasa3);
        q.push_back(i);
    }

    if b[0].0 < n {
        println!("Impossible");
    }
}