foo.cc: In function 'int main()':
foo.cc:35:18: warning: format '%d' expects argument of type 'int*', but argument 2 has type 'long int*' [-Wformat=]
     scanf("%d",&n);
                ~~^
foo.cc:37:22: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long int' [-Wformat=]
     printf("%d\n",ans);
                      ^
foo.cc:35:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~

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