Point(1) = {0,0,0,0.1};
Point(2) = {2,0,0,0.1};
Point(3) = {2,2,0,0.1};
Point(4) = {0,2,0,0.1};

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