You don't need the curly braces. Nice solution.

The joke with this kata is that you would normally just use System.Numerics, but you can't use it in your kata solution because (ha ha) you can't add a reference to System.Numerics here.

You will have to basically reimplement your own crappy version of BigInteger in order to make this work (or, at least, your own version of the BigInteger addition operation).

I am trying in C#. Which means I am using BigInteger.
To make it work I needed to add assembly System.Numeric.dll in my VS. But what to do to submit the solution for this Kata ? I am getting the following error:

"The type or namespace name 'Numerics' does not exist in the namespace 'System'. Are you missing `System.Numerics' assembly reference?"

Any help is appreciated.
Thanks.