/in/foo.cc: In function 'int calc(std::vector<bool>, ll)':
/in/foo.cc:54:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i + 1 < vec.size(); ++i)
                   ~~~~~~^~~~~~~~~~~~
/in/foo.cc:64:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < vec.size(); i += 2)
                     ~~^~~~~~~~~~~~
/in/foo.cc:71:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 1; i < vec.size(); i += 2)
                     ~~^~~~~~~~~~~~