--- CGALTriangulation2DKernel.H.old	2017-07-04 20:34:03.819767859 +0900
+++ CGALTriangulation2DKernel.H	2017-07-04 19:46:21.283195039 +0900
@@ -33,6 +33,7 @@
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
+#include "CGAL/number_utils.h"
 #include "CGAL/Delaunay_triangulation_2.h"
 
 #ifdef CGAL_INEXACT