foo.cc: In function 'int main()':
foo.cc:6:12: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for (scanf("%d", &n); n; n--)
       ~~~~~^~~~~~~~~~
foo.cc:8:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &x);
   ~~~~~^~~~~~~~~~
foo.cc:15:7: warning: 'num' may be used uninitialized in this function [-Wmaybe-uninitialized]
    num++;
    ~~~^~

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