foo.cc: In function 'int main()':
foo.cc:8:16: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int n,*a;scanf("%d",&n);
           ~~~~~^~~~~~~~~
foo.cc:11:13: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int x;scanf("%d",&x);
        ~~~~~^~~~~~~~~

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