foo.cc: In function 'void merge(std::vector<std::pair<int, int> >&, ll)':
foo.cc:29:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |  for(int i=0;i<res.size();i++)
      |              ~^~~~~~~~~~~

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