For years, the fabulously beautiful planet of Bethselamin increased its booming tourist industry without any worries at all. Alas, as is often the case, this was an act of utter stupidity, as it lead to a colossal cumulative erosion problem. Of course, what else could one expect with ten billion tourists per annum? Thus today the net balance between the amount you eat and the amount you excrete while on the planet is surgically removed from you body weight when you leave: so every time you got to the lavatory there it is vitally important to get a receipt.