Another year, another easter is coming – and the power just went out! here at the Easter Scientific Developers Inc. (easters.dev for short). Restarting the dye production has the top priority for sure. So you head into the server room to assess the situation. You try to log in to the server controlling the deep sea operation servers but you are prompted with a keypad, and of course you don't know the PIN. But you know that this server is also used as a print server. Looking around you spot the printing plates, amongst which, a resedential server demon tells you, are the plates used to test the printing. And one of the test prints was the PIN. To print something you need two plates stacked onto each other. Consider the following two plates, seperated by an empty line:
....#
.#.#.
..#.#
###..
.....
.....
.#..#
.##..
.....
...##
..#..
.#...
.#...
...##
To get the resulting print you look at each pixel of algae in the first plate and count the living (#) algae in the eight surrounding pixels in the second plate. Then, depending on if the algae in the first plate is alive, the result algae will be alive if there are 2 or 7 live algae surrounding it. If the algae was dead in the first plate, then the resulting pixel will be lit if there are 3, 4 or 6 algae alive in the surrounding pixels. So if you take those two plates from above and print with them you get a printing of a seven:
.....
.##..
..#..
.###.
..#..
..#..
.....
But there are more than two plates lying around. So you take the first two plates and print an image like above. Then you take that image as the base and take the next (3rd) plate and stack it ontop. Repeat this process until you get your final printing. To see if the algae is still ready to print compute the checksum first. Each pixel has its unique position number. Starting with 1 in the top-left, 2 the pixel right next to it, and in the case of our example plates 35 in the bottom right. To compute the checksum of a printing add all the positions of all alive algae. The digit 7 above has a checksum of 133.
What is the checksum of your final image?