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

Example Input: Retinoic acid regulates oral epithelial differentiation by _ mechanisms.
Example Output: two

Example Input: Carbon dioxide extinguishes fire by physically attacking all _ points of the fire triangle.
Example Output: three

Example Input: Toenails are similar, except that they grow _ times slower and are on the toes.
Example Output:
four