foo.c: In function 'main':
foo.c:28:18: warning: unused variable 'b' [-Wunused-variable]
  int n1,n2,p,q,a,b;
                  ^
foo.c:28:16: warning: unused variable 'a' [-Wunused-variable]
  int n1,n2,p,q,a,b;
                ^
foo.c:29:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf ("%d%d",&n1,&n2);
  ^~~~~~~~~~~~~~~~~~~~~~
foo.c:32:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf ("%d",&p);
   ^~~~~~~~~~~~~~~
foo.c:37:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf ("%d",&q);
   ^~~~~~~~~~~~~~~

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