sql - ORA-00933: SQL command not properly ended ORACLE

Question

select  
  (
    (select Count(country_isoname) from games.country where country_olympic_code is null)
    /
    (select Count(*) from games.country)
  ) * 100 as 'Percentage'
from 
  games.country;

I am currently trying to get the percentage but getting an error, syntax looks correct i think? PLease help!