foo.c: In function 'main':
foo.c:7:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ^~~~~~~~~~~~~~
foo.c:10:6: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
      scanf("%d",&a[i]);
      ^~~~~~~~~~~~~~~~~
foo.c:12:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&k);
  ^~~~~~~~~~~~~~
foo.c:6:5: warning: 'n' is used uninitialized in this function [-Wuninitialized]
     int a[n];
     ^~~

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