import std.algorithm;
import std.array;
import std.conv;
import std.range;
import std.stdio;
import std.string;

void main ()
{
	int n, len;
multitest_loop:
	while (readf (" %s %s", &n, &len) > 0)
	{
		readln;
		auto a = readln.split.map !(to !(int)).array;
		foreach (i; 0..n - 1)
		{
			if (a[i] + a[i + 1] >= len)
			{
				writeln ("Possible");
				auto d = iota (1, n).array;
				swap (d[i], d[$ - 1]);
				writefln ("%(%s\n%)", d);
				continue multitest_loop;
			}
		}
		writeln ("Impossible");
	}
}
