foo.cc: In function ‘void Merge(const std::vector<int>&, const std::vector<int>&, std::vector<int>&)’:
foo.cc:7:14: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    7 |     while (i < a.size() && j < b.size()) {
      |            ~~^~~~~~~~~~
foo.cc:7:30: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    7 |     while (i < a.size() && j < b.size()) {
      |                            ~~^~~~~~~~~~
foo.cc:14:14: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   14 |     while (i < a.size()) {
      |            ~~^~~~~~~~~~
foo.cc:17:14: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   17 |     while (j < b.size()) {
      |            ~~^~~~~~~~~~