temp=input().split()

N=int(temp[0])

L=int(temp[1])

a=[int(i) for i in input().split()]

flag=False

ans=[]



for i in range(N-1):

	if a[i]+a[i+1]>=L:

		print("Possible")

		flag=True

		ans.append(i)

		break

else:

	print("Impossible")



if flag==True:

	while ans[-1]>0:

		ans.append(ans[-1]-1)

	if ans[0]<N-1:

		ans.append(ans[0]+1)

		while ans[-1]<N-2:

			ans.append(ans[-1]+1)

	for i in range(N-2,-1,-1):

		print((ans[i]+1))
N,L=[int(i) for i in input().split()]

A=[int(i) for i in input().split()]



res=-1

for i in range(N-1):

	if A[i]+A[i+1]>=L:

		res=i

		break

if res!=-1:

	print("Possible")

	for i in range(res):

		print((i+1))

	for i in range(N-1,res,-1):

		print(i)

else:

	print("Impossible")

temp = input().split()
N = int(temp[0])
L = int(temp[1])
a = [int(i) for i in input().split()]
flag = False
ans = []
for i in range(N - 1):
    if a[i] + a[i + 1] >= L:
        print("Possible")
        flag = True
        ans.append(i)
        break
else:
    print("Impossible")
if flag == True:
    while ans[-1] > 0:
        ans.append(ans[-1] - 1)
    if ans[0] < N - 1:
        ans.append(ans[0] + 1)
        while ans[-1] < N - 2:
            ans.append(ans[-1] + 1)
    for i in range(N - 2, -1, -1):
        print((ans[i] + 1))

N, L = [int(i) for i in input().split()]
A = [int(i) for i in input().split()]
res = -1
for i in range(N - 1):
    if A[i] + A[i + 1] >= L:
        res = i
        break
if res != -1:
    print("Possible")
    for i in range(res):
        print((i + 1))
    for i in range(N - 1, res, -1):
        print(i)
else:
    print("Impossible")

-temp = input().split() -N = int(temp[0]) -L = int(temp[1]) -a = [int(i) for i in input().split()] -flag = False -ans = [] +N, L = [int(i) for i in input().split()] +A = [int(i) for i in input().split()] +res = -1 -    if a[i] + a[i + 1] >= L: -        print("Possible") -        flag = True -        ans.append(i) +    if A[i] + A[i + 1] >= L: +        res = i +if res != -1: +    print("Possible") +    for i in range(res): +        print((i + 1)) +    for i in range(N - 1, res, -1): +        print(i) -if flag == True: -    while ans[-1] > 0: -        ans.append(ans[-1] - 1) -    if ans[0] < N - 1: -        ans.append(ans[0] + 1) -        while ans[-1] < N - 2: -            ans.append(ans[-1] + 1) -    for i in range(N - 2, -1, -1): -        print((ans[i] + 1))