foo.c: In function 'main':
foo.c:18:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf ("%d%d%d",&n1,&n2,&n3);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:21:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf ("%d",&p);
   ^~~~~~~~~~~~~~~
foo.c:26:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf ("%d",&q);
   ^~~~~~~~~~~~~~~
foo.c:31:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf ("%d",&o);
   ^~~~~~~~~~~~~~~

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