It is a social and logical piece at the same time: each answer fits with the others until the party is secretly ordered. The solution doesn't count one-to-one squeezes; discover the structure that forces them.
The marriage handshake
Riddle statement
At a party there are several married couples. No one shakes hands with themselves or their own spouse.
You ask everyone else how many hands they have shaken and you get different answers.
How many hands has your spouse shaken?