foo.cc: In function 'void dts::main()':
foo.cc:66:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%lld",&rec[i]);
 ~~~~~^~~~~~~~~~~~~~~~
foo.cc:67:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%lld%lld",&a,&b);
 ~~~~~^~~~~~~~~~~~~~~~~~

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