Oops! Thanks, just distraction... It's that first I wanted to see the general solution to those kind of problems (and I gave the solution for a wrong one in the

Oops! Thanks, just distraction... It's that first I wanted to see the general solution to those kind of problems (and I gave the solution for a wrong one in the class), then I wanted to verify the C implementation of the solution with POPCNT like the OP seems to have done (I am writing the code)... Edit: ...and yes, it seems that brute-forcing (counting to one trillion) takes more time than I expected.