foo.c: In function 'main':
foo.c:11:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ^~~~~~~~~~~~~~
foo.c:12:22: 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]);
                      ^~~~~~~~~~~~~~~~~
foo.c:13:8: 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