foo.cc: In function 'int main()':
foo.cc:11:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   11 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
foo.cc:16:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   16 |    scanf("%d", &a[i]);
      |    ~~~~~^~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务