/in/foo.cc: In function 'void bfs()':
/in/foo.cc:16:30: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |                 for(int i=0;i<g[u].size();i++)
      |                             ~^~~~~~~~~~~~