foo.cc: In function ‘void dts::tr_dfs1(int, int)’:
foo.cc:28:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   28 |         for (int i=0;i<tr[now].s.size();i++)
      |                      ~^~~~~~~~~~~~~~~~~
foo.cc: In function ‘void dts::tr_dfs2(int, int)’:
foo.cc:48:27: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   48 |             for (int i=0;i<tr[now].s.size();i++)
      |                          ~^~~~~~~~~~~~~~~~~