foo.c: In function 'main':
foo.c:4:9: warning: unused variable 'n2' [-Wunused-variable]
  int n1,n2;
         ^~
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n1);
  ^~~~~~~~~~~~~~~
foo.c:10:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&a[n1]);
   ^~~~~~~~~~~~~~~~~~

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