Allow compiler specification from the env var.
Put problem 1 on it's own namespace.
Namespace problem 2.

Solution functions don't need to be static when they are namespaced
as they don't clash with eachother.
Prblem 1 functions not static.
Namespace problem 3.
Namespace problem 4.
Namespace problems 5 and 6.
Namespace problems 7, 8 and 9.
Namespace problem 10.
Namespace ant types in problem 11.
Namespace problems 12 and 13.
Namespace problem 14.
Namespace problems 15, 16 and18 (also comment it).
Namespace problem19.
Namespace problems 20 and 21.
Namespace problems 22 and 23.
Namespace problems 24 and 25.
Namespace problems 27 and 28.
Namespace problems 29, 30 and 31.
Namespace problems 48 and 67.