foo.cc: In function 'void dts::main()':
foo.cc:49:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 for (ll i=stk.back().i;i<e[stk.back().x].size();i++,stk.back().i=i)
                                        ~^~~~~~~~~~~~~~~~~~~~~~~
foo.cc:67:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 if (stk.back().i>=e[stk.back().x].size())
                     ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:36:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
                 scanf("%lld%lld%lld",&a,&b,&c);
                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。