foo.c: In function 'main':
foo.c:5:7: warning: variable 'a' set but not used [-Wunused-but-set-variable]
   int a[100];
       ^
foo.c:7:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&n);
   ^~~~~~~~~~~~~~

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