/in/foo.cc: In function 'double getd(int, int)':
/in/foo.cc:25:32: error: 'fabs' was not declared in this scope
     double x=fabs(a[i].x-a[j].x);
                                ^
/in/foo.cc:27:24: error: 'sqrt' was not declared in this scope
     return sqrt(x*x+y*y);
                        ^