BTW, you can easily simulate any linear random result, given two or more people.  Certainly close enough to random for game-play purposes.
For example, to simulate a d20: (1) one person (usually the DM) secretly picks a number between 1 and 20.  (2) At least one other person also picks a number between 1 and 20.  (3) Add the two (or more numbers together), mod 20, for the result.
I pick 13, you pick 5?  You got an 18.
I pick 19, you pick 19?  You got an 18.  (38 mod 20.)
I pick a 4, you pick a 19?  You got a 3.  (23 mod 20.)
It's very handy for randomizing in the absence of dice.  I also use something similar to this method when I'm DMing and don't want players to know my results as I roll.  (I don't use a screen.)  So I just pick a number as an addition to whatever I roll on the die.  They have no idea if my 18 on the die is an 18, or a 5, or what.  Stops a little bit of metagaming.