-print "Number of nodes after MergeNodes:", trias.NbNodes()
-print ""
-print "Number of elements before MergeEqualElements:"
-print "Edges : ", trias.NbEdges()
-print "Triangles : ", trias.NbTriangles()
-print "Quadrangles: ", trias.NbQuadrangles()
-print "Volumes : ", trias.NbVolumes()
-
-# merge elements
-trias.MergeEqualElements()
-print "Number of elements after MergeEqualElements:"
-print "Edges : ", trias.NbEdges()
-print "Triangles : ", trias.NbTriangles()
-print "Quadrangles: ", trias.NbQuadrangles()
-print "Volumes : ", trias.NbVolumes()
+print("Number of nodes after MergeNodes:", trias.NbNodes())
+print("")
+print("Number of elements before MergeEqualElements:")
+print("Edges : ", trias.NbEdges())
+print("Faces : ", trias.NbFaces())
+print("Volumes : ", trias.NbVolumes())
+
+# merge elements of the groups
+equalFaces = trias.FindEqualElements( [faceTriGroup, oppositeGroup, edgeGroup] )
+trias.MergeElements( equalFaces )
+print("Number of elements after MergeEqualElements:")
+print("Edges : ", trias.NbEdges())
+print("Faces : ", trias.NbFaces())
+print("Volumes : ", trias.NbVolumes())