foo.c: In function 'a2':
foo.c:15:6: warning: unused variable 'n' [-Wunused-variable]
   15 |  int n,k=0,a=0;
      |      ^
foo.c: In function 'main':
foo.c:31:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   31 |  scanf("%d",&x);
      |  ^~~~~~~~~~~~~~

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