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

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

Ex Output:
four


Ex Input:
Most crops require at least _ to eight hours of full sun a day to thrive.

Ex Output:
six


Ex Input:
Humans make _ major forms of interferon.

Ex Output:

three