foo.cc: In function 'int main()':
foo.cc:30:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   30 |  scanf("%d%d%d",&n,&m,&k);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~
foo.cc:32:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   32 |  scanf("%d%d%d",&a[i].x,&a[i].y,&a[i].w);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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