foo.cc: In function 'int main()':
foo.cc:7:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<k.size();i++){
                 ~^~~~~~~~~
foo.cc:16:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int j=2;j<a.size();j++){
                     ~^~~~~~~~~

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

{"receive":"2020-07-09T12:39:02.963Z","handle":"2020-07-09T12:39:02.963Z","cache_start":"2020-07-09T12:39:02.972Z","read_cases":"2020-07-09T12:39:03.103Z","judge":"2020-07-09T12:39:03.103Z","done":"2020-07-09T12:39:04.212Z"}