foo.cc: In function 'void dts::tr_dfs1(int, int)':
foo.cc:28:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         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 between signed and unsigned integer expressions [-Wsign-compare]
             for (int i=0;i<tr[now].s.size();i++)
                          ~^~~~~~~~~~~~~~~~~
foo.cc: In function 'void dts::main()':
foo.cc:208:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&n);
         ~~~~~^~~~~~~~~
foo.cc:210:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d",&data[i]);
             ~~~~~^~~~~~~~~~~~~~~
foo.cc:216:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d%d",&x,&y);
             ~~~~~^~~~~~~~~~~~~~
foo.cc:223:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d\n",&m);
         ~~~~~^~~~~~~~~~~
foo.cc:228:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%c%d%d\n",&K,&x,&y);
             ~~~~~^~~~~~~~~~~~~~~~~~~~~

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