foo.c:3:1: warning: return type defaults to 'int' [-Wimplicit-int]
    3 | fun(int n)
      | ^~~
foo.c:11:1: warning: return type defaults to 'int' [-Wimplicit-int]
   11 | main()
      | ^~~~
foo.c: In function 'main':
foo.c:14:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   14 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~

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