foo.cc: In function 'void init()':
foo.cc:43:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   43 |     scanf("%d%d",&m,&n);
      |     ~~~~~^~~~~~~~~~~~~~
foo.cc:45:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   45 |         scanf("%d",&a[i]);
      |         ~~~~~^~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务