There are three pillars X, Y and Z of different heights. Three spiders A, B and C start to climb on these pillars simultaneously. In one chance A climbs on X 5 cm but slips down 1 cm. B climbs on Y 6 cm but slips down 3 cm. C climbs on Z 7 cm but slips down 2 cm. If each requires 50 chances to reach the top of the pillar, what is the height of the shortest pillar?
