Hint:
My C++ code won't type check. Can you fix that for me?
Note: you will need to set -ftemplate-depth=10000 when compiling.
This was a C++ rev challenge involving the template system. It had an input which was the flag, and an input that was the program. It created lists using some variadic templates, and then could use stack like behavior by popping or pushing by invoking further templates.