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

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

Example Input: Optical isomers differ in the arrangement of _ groups around a chiral carbon.
Example Output: four

Example Input: Soy contains at least _ compounds that inhibit pigment formation.
Example Output:
two