foo.cc: In function 'double getd(int, int)':
foo.cc:24:14: error: 'fabs' was not declared in this scope; did you mean 'labs'?
   24 |     double x=fabs(a[i].x-a[j].x);
      |              ^~~~
      |              labs
foo.cc:26:12: error: 'sqrt' was not declared in this scope
   26 |     return sqrt(x*x+y*y);
      |            ^~~~

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