foo.c: In function 'main':
foo.c:5:6: warning: unused variable 'ret' [-Wunused-variable]
    5 |  int ret,num;
      |      ^~~
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    7 |  scanf("%d",&input);
      |  ^~~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务