l=6;
h=6;
w=1;
c=0.5;

Point(1) = {0, 0, 0, c};
Point(2) = {l, 0, 0, c};
Point(3) = {0, h, 0, c};
Point(4) = {l, h, 0, c};

Line(1) = {1, 2};
Line(2) = {2, 4};
Line(3) = {4, 3};
Line(4) = {3, 1};
Line Loop(5) = {3, 4, 1, 2};
Plane Surface(6) = {5};
Physical Surface(7) = {6};
Recombine Surface {6};

