Abyssinians and Somalis organise their General Secret Assembly.
At the entrance door, one of them acts as the guard,
in charge of asking the newcomers to say a password before being allowed to come in.

A first aby arrives. The guard looks at him and asks him "Six ?",
the little aby answers "Three", and the guard lets him in.
Then a somali arrives, the guard asks him "Three ?",
the somali answers "Five" and the guard lets him in.
A bit later, another aby comes by the door, the guard asks him "Nine ?",
the aby answers "Four" and the guard lets him in.

Now a somali arrives, the guard asks him "Five ?"
What answer must the somali provide to be let in ?