foo.c: In function 'main':
foo.c:20:8: warning: unused variable 'j' [-Wunused-variable]
   20 |  int i,j,n1,n2;
      |        ^
foo.c:21:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   21 |  scanf("%d%d",&n1,&n2);
      |  ^~~~~~~~~~~~~~~~~~~~~
foo.c:23:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   23 |   scanf("%d",&a1[i]);
      |   ^~~~~~~~~~~~~~~~~~
foo.c:26:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   26 |   scanf("%d",&a2[i]);
      |   ^~~~~~~~~~~~~~~~~~

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