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

Example Input: Metals often crystallize in a _ dimensional version of the hexagonal closest packed structure.
Example Output: three

Example Input: Liquid crystals lack the full _ dimensional position and orientation order of ordinary crystals.
Example Output: three

Example Input: Ants also have the characteristic _ part body of an insect.
Example Output:
three