foo.cc: In function 'int main()':
foo.cc:37:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&x1,&y1);
  ~~~~~^~~~~~~~~~~~~~~~
foo.cc:38:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&x2,&y2);
  ~~~~~^~~~~~~~~~~~~~~~

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