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

Example Input: Giraffes have two horns and _ or three knobs.
Example Output: two

Example Input: Acrobats mount a single bicycle until _ people in all are stacked on top of it.
Example Output: ten

Example Input: Morocco has _ perennial rivers and many dams have been built with potential for power generation.
Example Output:
four