foo.cc: In function 'int main(int, const char**)':
foo.cc:15:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &n, &m);
                          ^
foo.cc:17:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &a, &b);
                              ^

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

Cannot connect to sandbox service
Error: Cannot connect to sandbox service
    at exports.run (/root/jd5/judger/sandbox/executionServer.js:77:15)
    at process._tickCallback (internal/process/next_tick.js:68:7)
[]