X 2 1 x b

X 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x b
X 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x b
X 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x bX 2 1 x b