foo.c: In function 'main':
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d %d",&a,&b,&c);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:11:2: warning: ignoring return value of 'system', declared with attribute warn_unused_result [-Wunused-result]
  system("pause");
  ^~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务