The problem says "The standard output should contain in its
only line a real number with two digits precision (after a
decimal point)"
So the result must not be rounded and we can't directly
use ":0:2".But in fact when i output the result with the
code "((result*100-frac(result*100))/100:0:2" , it says
wrong!
Finally hopelessly,i recomposed the code with
only ":0:2".Then it accepted!
Please check it.