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.