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

Ex Input:
New species are believed to arrive in the Mediterranean at the rate of _ to five annually.

Ex Output:
four

Ex Input:
Intramural football consists of _ leagues.

Ex Output:
three

Ex Input:
Atoms are most stable when they have _ electrons in their outer electron energy level.

Ex Output:
eight