Mesh.Format=2;
Point(1) = {0, 0, 0, 5};
Point(2) = {120, 0, 0, 5};
Point(3) = {120, 60, 0, 5};
Point(4) = {0, 60, 0, 5};
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 1};
Line Loop(9) = {1, 2, 3, 4};
Plane Surface(9) = {9};
// gmsh -2 -format mesh -string "Mesh.SaveElementTagType=2; -o polygon.3.mesh polygon.geo
// gmsh -2 -Mesh.Format "Mesh.SaveElementTagType=2; -o polygon.3.mesh polygon.geo;

