/in/foo.cc: In function 'void merge1(std::vector<int>&)':
/in/foo.cc:19:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   19 |         for (int i = 0; i < v.size() - 1; i++)
      |                         ~~^~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:38:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |         for (int i = 0; i < v1.size(); i++)
      |                         ~~^~~~~~~~~~~
/in/foo.cc:41:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   41 |         for (int i = 0; i < v2.size(); i++)
      |                         ~~^~~~~~~~~~~