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

Ex Input:
Sharks have five to _ gill slits.

Ex Output:
seven

Ex Input:
Reds can benefit from seven to _ years' aging .

Ex Output:
nine

Ex Input:
Natural uranium is a mixture of _ isotopes, or atomic strains, of the element.

Ex Output:
three