/in/foo.cc: In function 'int main()':
/in/foo.cc:33:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |     for (int i = 0; i < xs.size() - 1; ++i) {
      |                     ~~^~~~~~~~~~~~~~~
/in/foo.cc:37:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |         for (int j = 0; j < ys.size() - 1; ++j) {
      |                         ~~^~~~~~~~~~~~~~~