/in/foo.cc: In function 'void dts::tr_dfs1(int, int, int)':
/in/foo.cc:28:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0;i<tr[now].s.size();i++)
                      ~^~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'void dts::tr_dfs2(int, int)':
/in/foo.cc:48:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i=0;i<tr[now].s.size();i++)
                          ~^~~~~~~~~~~~~~~~~