foo.cc: In function 'int un(int, int)':
foo.cc:43:1: warning: no return statement in function returning non-void [-Wreturn-type]
   43 | }
      | ^
foo.cc: In function 'int main()':
foo.cc:75:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   75 |                 for(int k=0; k<q[i].size(); k++) {
      |                              ~^~~~~~~~~~~~

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