N,L = list(map(int,input().split()))

A = list(map(int,input().split()))

A.insert(0,0)

flag = 0

for i in range(1,N):

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

        flag = i

        break

if flag == 0:

    print("Impossible")

else:

    print("Possible")

    if flag==1:

        for i in range(N-1,0,-1):

            print(i)

    else:

        for i in range(1,flag):

            print(i)

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

            print(i)
N,L = list(map(int,input().split()))

A = list(map(int,input().split()))

A.insert(0,0)

cmax = 0

ind = -1

for i in range(1,N):

    if A[i]+A[i+1]>cmax:

        cmax = A[i]+A[i+1]

        ind = i

if cmax>=L:

    print("Possible")

    for i in range(1,ind):

        print(i)

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

        print(i)

else:

    print("Impossible")
N, L = list(map(int, input().split()))
A = list(map(int, input().split()))
A.insert(0, 0)
flag = 0
for i in range(1, N):
    if A[i] + A[i + 1] >= L:
        flag = i
        break
if flag == 0:
    print("Impossible")
else:
    print("Possible")
    if flag == 1:
        for i in range(N - 1, 0, -1):
            print(i)
    else:
        for i in range(1, flag):
            print(i)
        for i in range(N - 1, flag - 1, -1):
            print(i)

N, L = list(map(int, input().split()))
A = list(map(int, input().split()))
A.insert(0, 0)
cmax = 0
ind = -1
for i in range(1, N):
    if A[i] + A[i + 1] > cmax:
        cmax = A[i] + A[i + 1]
        ind = i
if cmax >= L:
    print("Possible")
    for i in range(1, ind):
        print(i)
    for i in range(N - 1, ind - 1, -1):
        print(i)
else:
    print("Impossible")

-flag = 0 +cmax = 0 +ind = -1 -    if A[i] + A[i + 1] >= L: -        flag = i -        break -if flag == 0: +    if A[i] + A[i + 1] > cmax: +        cmax = A[i] + A[i + 1] +        ind = i +if cmax >= L: +    print("Possible") +    for i in range(1, ind): +        print(i) +    for i in range(N - 1, ind - 1, -1): +        print(i) +else: -else: -    print("Possible") -    if flag == 1: -        for i in range(N - 1, 0, -1): -            print(i) -    else: -        for i in range(1, flag): -            print(i) -        for i in range(N - 1, flag - 1, -1): -            print(i)