Performance & Recursion

How can you count all the participants in an auditorium if you don't have sensors, check-in processes or access control? Option 1: Use my eyes and my mind to count them one by one: 1,2,3,4... Option 2: Count by twos, like 2,4,6,8,... Option 3: Ask the participants to follow these instructions: Stand up and think of the number 1 Pair off with someone standing, add their number to yours, and remember the sum One of you should then sit down If still standing, go back to step 2. The final person sta