foo.cc: In function 'void input_data()':
foo.cc:17:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d%d",&m,&n,&k);
 ~~~~~^~~~~~~~~~~~~~~~~~~
foo.cc:21:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d",&x1[i],&y1[i]);
 ~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:25:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d",&x2[i],&y2[i]);
 ~~~~~^~~~~~~~~~~~~~~~~~~~~~

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