foo.cc: In function 'int main()':
foo.cc:19:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&n,&m);
     ~~~~~^~~~~~~~~~~~~~
foo.cc:23:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&x,&y);
         ~~~~~^~~~~~~~~~~~~~
foo.cc:26:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&k);
     ~~~~~^~~~~~~~~
foo.cc:36:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d%d",&x,&y);
             ~~~~~^~~~~~~~~~~~~~

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