foo.cc: In function ‘void dfs(int)’:
foo.cc:9:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    9 |         for(int i=0; i<e[x].size(); i++) {
      |                      ~^~~~~~~~~~~~
foo.cc:16:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   16 |         for(int i=0; i<a.size(); i++)
      |                      ~^~~~~~~~~