foo.c: In function 'main':
foo.c:7:17: error: 'n' undeclared (first use in this function)
    7 |         int num[n];
      |                 ^
foo.c:7:17: note: each undeclared identifier is reported only once for each function it appears in
foo.c:8:21: error: 'a' undeclared (first use in this function)
    8 |         scanf("%d",&a);
      |                     ^
foo.c:7:13: warning: unused variable 'num' [-Wunused-variable]
    7 |         int num[n];
      |             ^~~

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