foo.c: In function 'main':
foo.c:20:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ^~~~~~~~~~~~~~~
foo.c:23:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &arr[i]);
   ^~~~~~~~~~~~~~~~~~~~
foo.c:25:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &k);
  ^~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务