P tb

P tbP tbP tbP tb
P tbP tbP tbP tbP tbP tbP tbP tb
P tbP tbP tbP tbP tbP tbP tbP tbP tbP tbP tbP tb
P tbP tbP tbP tbP tbP tbP tbP tbP tbP tbP tbP tbP tbP tbP tbP tb
P tbP tbP tbP tbP tbP tbP tbP tb