A man suffers from terrible constipation, and decides to go to his doctor. After the man describes his sorrowful condition, the doctor decides to prescribe him a laxative. He grabs a paper and a pencil and starts doing some calculations. He asks the man, "How are you gonna go home?", to which the man replies "I'll walk." The doctor then tell him there's a public toilet just 10 minutes away. He takes into account the man's speed of walking, how near the toilet is, whether it may be occupied and so on. After carefully calculating something for a solid 15 minutes, he measures a precise amount of the laxative and asks the man to consume it in the clinic itself, and tells him to immediately leave for his home, and report back on the status of success later on. 30 minutes later, the man comes back to the doctor's office with a very uncomfortable expression on his face, and walking weirdly. He says "Doc, the laxative worked quite well, but... do you have 50 cents?''