/in/foo.cc: In function 'void Output(const std::vector<long int>&)':
/in/foo.cc:11:24: warning: comparison of integer expressions of different signedness: 'long int' and 'std::vector<long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   11 |     for (long i = 1; i < a.size(); i++) {
      |                      ~~^~~~~~~~~~