foo.cc: In function 'int main()':
foo.cc:58:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lf%lf",&x[i],&y[i]);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:64:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lf%lf%lf",&nx,&ny,&nv);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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