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

Ex Input:
Rats multiply _ times as fast as cats.

Ex Output:
four


Ex Input:
Ozone leaves _ by-products except pure oxygen.

Ex Output:
no


Ex Input:
Natural ytterbium is a mixture of _ stable isotopes, with seven other unstable isotopes known.

Ex Output:

seven