foo.c: In function 'super':
foo.c:37:1: warning: control reaches end of non-void function [-Wreturn-type]
   37 | }
      | ^
foo.c: In function 'main':
foo.c:42:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   42 |   scanf("%d",&x);
      |   ^~~~~~~~~~~~~~
foo.c: In function 'prime':
foo.c:8:4: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
    8 |    for (i=2;i<=k;i++)
      |    ^~~

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