In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

Ex Input:
Falcons are roughly divisible into three or _ groups.

Ex Output:
four

Ex Input:
Pelycosaurs are a paraphyletic group of _ primitive families of synapsids.

Ex Output:
six

Ex Input:
Additive color combines the _ colors to make white.

Ex Output:
three