foo.c: In function 'main':
foo.c:8:17: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  int n1, n2, i; scanf("%d%d", &n1, &n2);
                 ^~~~~~~~~~~~~~~~~~~~~~~
foo.c:10:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &a1[i]);
   ^~~~~~~~~~~~~~~~~~~
foo.c:12:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &a2[i]);
   ^~~~~~~~~~~~~~~~~~~

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