Before the game begins everyone who is playing have to agree on a number under ten.
In the beginning it doesn't matter who starts but they start with the number one.
Play goes left from there.
Whenever a number that is a multiple of the chosen number or has the chosen number in it comes up then the player who gets that turn has to say Va-fonculo.
The play then reverses directions and continues until someone fucks up by either saying the number instead of Va-fonculo or accusing someone of slipping up and being wrong.
This game will definately mess you up because it goes quickly and surprisingly your math skills deteriorate when you drink.
If my explanation was lame then here is an example: the number decided upon is, let's say seven and a big V will represent when someone is supposed to say Va-fonculo.
Little arrows will indicate direction changes: 1,2,3,4,5,6,V <- 8,9,10,11,12,13,V-> 15,16, V <- 18,19,20, V -> 22,23.....etc.
It's fun. Especially when the people play!