foo.c: In function 'main':
foo.c:8:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ^~~~~~~~~~~~~~
foo.c:10:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a[i]);
   ^~~~~~~~~~~~~~~~~
foo.c:11:8: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  int k;scanf("%d",&k);
        ^~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务