/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:33:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0; i<connections[u].size(); ++i)
                  ~^~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'void rebuild(int)':
/in/foo.cc:81:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int j=0; j<connections[i].size(); ++j)
                      ~^~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:147:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<ans_arr[0].size();++i)
                     ~^~~~~~~~~~~~~~~~~~