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

Ex Input:
Retinoic acid regulates oral epithelial differentiation by _ mechanisms.

Ex Output:
two


Ex Input:
Rheas are brownish instead of black like the ostrich and have _ toes instead of two.

Ex Output:
three


Ex Input:
All loci have _ or two alleles.

Ex Output:

one