Question: A person decides to shake hands with six different people on a certain day. The next day, each of the six people will shake hands with six different people. The process continues until every person in the United States has shaken someone's hand. How many days will it take until everyone in the United States has shaken hands once? Assume that once a person shakes hands with six different people, he or she does not shake hands again. According to the 2000 census, the population of the United States is 281,421,906.