foo.cc: In function 'int main()':
foo.cc:11:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=1; i<l; i++){
                 ^
foo.cc:15:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0; i<l; i++){
                 ^

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

{"receive":"2020-07-02T13:35:00.945Z","handle":"2020-07-02T13:35:00.945Z","cache_start":"2020-07-02T13:35:00.951Z","read_cases":"2020-07-02T13:35:01.106Z","judge":"2020-07-02T13:35:01.108Z","done":"2020-07-02T13:35:02.782Z"}