foo.cc: In function 'int main()':
foo.cc:15:38: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   15 |                         for(int k=0;k<a.size();k++){
      |                                     ~^~~~~~~~~
foo.cc:7:13: warning: unused variable 'num' [-Wunused-variable]
    7 |         int num=0;
      |             ^~~

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