A long time ago I saw this riddle, and it was really mind blowing how difficult it was to solve, but how logic and easy it seems once you know the answer.

So I'll give you guys this riddle. And see if you can solve it.

Please don't be a cheap ass cheater by googling it. Although I can't stop you from doing so, it ruins the fun for yourself wouldn't it?

**Well then, the riddle is as follows:**Below are a few lines of random numbers. Or well, random? They aren't random at all! In fact, each row of numbers is written with a certain rule applied to the previous row of numbers.

Now, your challenge is simple:

- Figure out what this certain rule is, that is applied on each row of numbers.

- Use this rule to fill in the final row of numbers.

Good luck! Here are the number rows:

1

11

21

1211

1231

131221

132231

232221

134211

14131231

14231241

? ? ? ? ? ? ? ? (Fill in next row here.)