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

Ex Input:
Gravity is the weakest of all _ forces but unlike the others it has an unlimited range.

Ex Output:
four


Ex Input:
Phosphates are made of _ phosphorus atom surrounded by four oxygen atoms.

Ex Output:
one


Ex Input:
Female dogs go into heat twice a year, lasting anywhere from _ to fifteen days.

Ex Output:

three