foo.cc: In function 'int main()':
foo.cc:8:15: warning: format '%c' expects argument of type 'char*', but argument 2 has type 'char (*)[10000]' [-Wformat=]
  scanf("%c",&a);
             ~~^
foo.cc:8:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%c",&a);
  ~~~~~^~~~~~~~~

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