a = 2;
b = 1;
R = 0.25;
ssize = 0.05;

Point(1) = { 0, 0, 0, ssize};
Point(2) = { a, 0, 0, ssize};
Point(3) = { 0, b, 0, ssize};
Point(4) = { a, b, 0, ssize};

Point(5) = { a/2, b/2, 0, ssize};
Point(6) = { a/2+R, b/2, 0, ssize};
Point(7) = { a/2, b/2+R, 0, ssize};
Point(8) = { a/2-R, b/2, 0, ssize};
Point(9) = { a/2, b/2-R, 0, ssize};

Line(1) = {1,2};
Line(2) = {2,4};
Line(3) = {4,3};
Line(4) = {3,1};
Circle(5) = {6,5,7};
Circle(6) = {7,5,8};
Circle(7) = {8,5,9};
Circle(8) = {9,5,6};

Line Loop(9) = {5,6,7,8};
Plane Surface(10) = {9};
Line Loop(11) = {3,4,1,2};
Plane Surface(12) = {11,9};

Physical Surface(1) = {10}; // trou
Physical Surface(2) = {12}; // exterieur

Physical Line(3) = {1,2,3,4}; // frontiere

