[Gmsh] 3D mesh between/inside extruded cubes

[Szalontai Levente]

Dear GMSH Users,

I'm a beginner of using GMSH. The following problem I have: I make a big 
cube and a little cube inside of the big cube, both of them made by 
using extrusion command.
(see the attached file) When I want to generate the 3D mesh, then it 
isn't meshing the volume among the big and little cube, but only the 
volume inside the little cube. What do I wrong?

-- 
Üdvözlettel,
Szalontai Levente
---
Best Regards,
Levente Szalontai

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msize=0.8;
//LITTLE BOX
Point(0)={1,1,-2,msize};
Point(1)={-1,1,-2,msize};
Point(2)={-1,-1,-2,msize};
Point(3)={1,-1,-2,msize};

Line(4)={0,1};
Line(5)={1,2};
Line(6)={2,3};
Line(7)={3,0};

Line Loop(8) = {4,5,6,7};
Plane Surface(9) = {8};
littlebox [] = Extrude{0,0,4}{Surface{9};};

//BIG BOX
Point(100)={2,2,-4,msize};
Point(101)={-2,2,-4,msize};
Point(102)={-2,-2,-4,msize};
Point(103)={2,-2,-4,msize};

Line(104)={100,101};
Line(105)={101,102};
Line(106)={102,103};
Line(107)={103,100};

Line Loop(108) = {104,105,106,107};
Plane Surface(109) = {108};
bigbox [] = Extrude{0,0,8}{Surface{109};};

// Volume(3)={1,2};