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

Ex Input:
Prostate cancer is categorized in _ stages.

Ex Output:
four

Ex Input:
Induction also operates early in development, even before the _ layered embryo forms.

Ex Output:
three

Ex Input:
Some parents do favour contact for children starting at _ years old.

Ex Output:
eight