Hiding in the shadows, you are spying on the doorkeeper to a facility you wish to infiltrate. In excitement, you observe the first visitor arrive and hear the doorkeeper simply saying “six” to him. The visitor responds “three” and with that gains access. A couple of hours later a second visitor reaches the doorkeeper, who greets him with the word “twelve”. The visitor responds “six” and the doorkeeper steps aside, granting him access. Feeling confident, you walk up the doorkeeper, who says “ten” to you.

What do you say in response?

[Solution]