/in/foo.cc: In function 'int main()':
/in/foo.cc:41:16: 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<p2.size();i++)
      |               ~^~~~~~~~~~