a = 25 --sides
c = 2 --height (max is 12)

function selectBlock()
if turtle.getItemCount() < 1 then
i = 1
while true do
turtle.select(i)
i = i + 1
if turtle.getItemCount() > 0 then
return true
end
if i > 16 then
return false
end
end
end
end

turtle.turnLeft()
turtle.turnLeft()
for z=1,c do
for num=1,4 do
for x=2,a do
selectBlock()
if num < 4 or x < a then
if not turtle.back() then
os.shutdown()
end
turtle.place()
end
end
turtle.turnLeft()
end
turtle.up()
selectBlock()
turtle.placeDown()
turtle.turnRight()
turtle.back()
turtle.turnLeft()
end