/in/foo.cc: In function 'double getd(int, int)':
/in/foo.cc:57:77: error: 'sqrt' was not declared in this scope
  return sqrt((a[i].x-a[j].x)*(a[i].x-a[j].x)+(a[i].y-a[j].y)*(a[i].y-a[j].y));
                                                                             ^