/in/foo.cc: In function 'void dts::dfs(std::vector<long long int>)':
/in/foo.cc:24:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (ll i=0;i<rec.size();i++)
                ~^~~~~~~~~~~
/in/foo.cc:25:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (ll j=i+1;j<rec.size();j++)
                   ~^~~~~~~~~~~
/in/foo.cc:27:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
      for (ll k=0,l=0;k<rec.size();k++)
                      ~^~~~~~~~~~~