Once upon a time there was a sacred temple hidden in the deep mountains, in which believers gathered to exercise meditation to become saints. The believers sat in a circle facing each other while meditating during the day, and retired to their separate rooms during the night. God would mark the foreheads of some believers one night when they were sound in sleep. Those who had a mark on their foreheads would become saints once they walked out of the temple, while those who walked out without a mark on their foreheads would starve to death in the wilderness. The believers could see the faces of all other believers except his or her own. There was no way for them to see their own faces and they never communicate to each other in any way. God would choose at least one from the believers. How could those who were chosen by God find out that they were the chosen ones? How many days would it take before all the chosen ones walked out of the temple, if God marked N foreheads?