foo.cc: In function 'int main()':
foo.cc:21:14: warning: format '%d' expects argument of type 'int*', but argument 2 has type 'int' [-Wformat=]
  scanf("%d",n);
              ^
foo.cc:23:18: warning: format '%d' expects argument of type 'int*', but argument 2 has type 'int' [-Wformat=]
   scanf("%d",b[i]);
              ~~~~^
foo.cc:26:2: error: 'prinf' was not declared in this scope
  prinf("%d",ans);
  ^~~~~
foo.cc:26:2: note: suggested alternative: 'printf'
  prinf("%d",ans);
  ^~~~~
  printf
foo.cc:21:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",n);
  ~~~~~^~~~~~~~
foo.cc:23:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",b[i]);
   ~~~~~^~~~~~~~~~~

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