n = io.read("*number")
l = io.read("*number")
pre = -1
max = 0
maxindex = -1
index = 0
for x in string.gmatch(io.read("*all"), "%S+") do
cur = tonumber(x)
if (pre + cur) > max then
max = pre + cur
maxindex = index
end
pre = cur
index=index+1
end
if max >= l then
print("Possible")
for i=1,maxindex-1,1 do io.write(i, " ") end
for i=n-1,maxindex+1,-1 do io.write(i, " ") end
io.write(maxindex,"\n")
else
print("Impossible")
end