X1X2X3X4X1

X1 X2 X3 X4 X1

X1 X2 X3 X4 X4 X1 X2 X3

X1 X2 X3 X4

X1 X2 X3 X4 X4

X1 X2 X3 X4 X1

    

X1 X2 X3 X4 X1