What number should be placed in that last slot? [closed]

I came across a very difficult puzzle. What number should be placed in that last slot? I only know 16 is not the correct answer, because 11 is before 10.

• Is this one of those (rot13) uggcf://ra.jvxvcrqvn.bet/jvxv/15_chmmyr? If so this seems like it's one of those impossible-to-solve configurations. – Hugh Jul 3 at 6:03
• No, it is not an impossible-to-solve configuration. – James Jul 3 at 6:08
• (rot13) Gnxr 15 guna chg 0 gurer, guna lbh pna fbyir gur 15 chmmyr – Jamal Senjaya Jul 3 at 7:05
• Welcome. Please can you clarify what the puzzle is. Have you put those numbers in that order, and we have find an extra number? Have you seen a picture of this puzzle and want to know how it works? To me this looks like a well-known type of puzzle where the task is to move the blocks around to get them in the correct order. There is meant to be a gap to allow room to slide blocks. In that case the final number doesn't exist. Please explain, thanks. – chasly - supports Monica Jul 3 at 11:52
• @James - chasly above has done a good job trying to clear things up, but I'll extend on that. I believe that the "goal" of this puzzle is to slide the tiles around until they are in numerical order - 1 in the top left, reading left-to-right and top-to-bottom. It has been shown that some inital starting positions are "unsolvable" - link 1, link 2 – Hugh Jul 3 at 19:22