foo.cc: In function 'int main()':
foo.cc:53:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~
foo.cc:56:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%lf %lf",&ar[i].x,&ar[i].y);
             ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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