foo.c: In function 'main':
foo.c:27:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ^~~~~~~~~~~~~~
foo.c:28:22: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  for(int i=0;i<n;++i)scanf("%d",a+i);
                      ^~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务