foo.cc: In function 'int main()':
foo.cc:17:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   17 |  freopen("secret.in","r",stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
foo.cc:18:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   18 |  freopen("secret.out","w",stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务