foo.c: In function 'main':
foo.c:19:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   19 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
foo.c:20:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   20 |  scanf("%d %d", &a, &b);
      |  ^~~~~~~~~~~~~~~~~~~~~~
foo.c:23:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   23 |   scanf("%d", &b);
      |   ^~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务