foo.cc: In function 'void init()':
foo.cc:17:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   17 |     scanf("%d%d",&m,&n);
      |     ~~~~~^~~~~~~~~~~~~~
foo.cc:19:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   19 |         scanf("%d",&a[i]);
      |         ~~~~~^~~~~~~~~~~~

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