/in/foo.cc: In function 'void dts::tr_dfs1(int, int)':
/in/foo.cc:31:17: 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:52:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i=0;i<tr[now].s.size();i++)
                 ~^~~~~~~~~~~~~~~~~