foo.c: In function 'main':
foo.c:13:17: error: 'a' undeclared (first use in this function)
     printf("%d",a[i]);
                 ^
foo.c:13:17: note: each undeclared identifier is reported only once for each function it appears in
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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