A friend came up to me today with a deck of cards, and put these 6 into a group:
2 3 5 7 J K
The other 7 values went into another group:
A 4 6 8 9 10 Q
He then challenged me to find the reason for the groupings.
"That's easy," I said. "The first group is primes!"
"Well, yes, but not what I had in mind," he replied, with a twinkle in his eye. "This property isn't mathematical!"
I thought for a while, then exclaimed, "O!"
What was the property?