foo.cc: In function 'void dts::dfs(std::vector<long long int>)':
foo.cc:24:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (ll i=0;i<rec.size();i++)
                         ~^~~~~~~~~~~
foo.cc:25:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 for (ll j=i+1;j<rec.size();j++)
                               ~^~~~~~~~~~~
foo.cc:27:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     for (ll k=0,l=0;k<rec.size();k++)
                                     ~^~~~~~~~~~~
foo.cc: In function 'void dts::main()':
foo.cc:63:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%s",s);
             ~~~~~^~~~~~~~

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