You wake up in a cell after a party. You just remember the beginning of the night: you talked to your friends, you drank some alcohol, and then you blacked out.
You stand up and look around you: you are in a small empty room with no window and a door locked with a numeric keypad.

You approach the keypad and notice a piece of paper:

You'd better not try to steal my spaghetti recipe again!
I'll let you out if you can solve this puzzle:


are all acceptable numbers, but



If you find the key, you can live. (And if you fail, my pet elephant will make sure you wish you weren't alive...).


What is the key to the puzzle?

Hint :

The key is 2-char long

(Note: This isn't a lateral-thinking question, so there's no need for ridiculous answers like "I punch through the wall".)

  • 2
    $\begingroup$ I edited it to fix the grammar and spelling. Wasn't sure what you meant by the "key to the puzzle" (I'm guessing the pattern has some number that stands out), and I assumed a "digicode" was a keypad with numbers on it. $\endgroup$
    – Deusovi
    Commented Jul 28, 2015 at 10:29
  • $\begingroup$ @Deusovi: Great clean up. I was itching to clean it up too, but saw that it was too much work, so I gave up. $\endgroup$
    – CodeNewbie
    Commented Jul 28, 2015 at 10:34
  • $\begingroup$ So just to confirm, the key is a single number input on the keypad? $\endgroup$
    – Set Big O
    Commented Jul 28, 2015 at 12:39
  • $\begingroup$ So is I FALCONPUNCH through a wall still valid? $\endgroup$ Commented Jul 28, 2015 at 12:55
  • $\begingroup$ @Geobits exactly $\endgroup$ Commented Jul 28, 2015 at 12:56

1 Answer 1


I'd do some quick addition and type


because each number on the left

turns into 4 if you repeatedly add digits until you get a single digit (49 -> 4+9=13 -> 1+3=4)

and each on the right

results in 2 (83 -> 8+3=11 -> 1+1=2)

In the invalid pairs, at least one of them is wrong.

Also, you know, it's the answer, assuming you know the question.

  • 1
    $\begingroup$ Well play, well play :) $\endgroup$ Commented Jul 28, 2015 at 13:42
  • 1
    $\begingroup$ For all that may need a hint to the answer :) 42 $\endgroup$ Commented Jul 28, 2015 at 13:52
  • $\begingroup$ That's a pretty blatant hint :P $\endgroup$
    – Set Big O
    Commented Jul 28, 2015 at 14:08
  • $\begingroup$ This makes me sad, I was adding digits and I was like of so the left needs to sum to more than the right. But that didn't hold. AAND I just shoulda paid some attention to the actual sums... (and then repeated). but gj. $\endgroup$ Commented Jul 28, 2015 at 14:49
  • $\begingroup$ @Goinghamateur To be fair, I should credit qwertylpc somehow. His deleted answer led me to the idea. I just don't know how to appropriately credit deleted answers, since many users can't see it. Well, besides this roundabout way, I guess. $\endgroup$
    – Set Big O
    Commented Jul 28, 2015 at 14:52

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