It's an election year, and volunteers are putting posters up for their favorite candidates. There is a long street in your town with 1,000 houses in a row.The first volunteer who passes through this street has time to put a poster on the door of every house. The second volunteer comes a bit later, and only has time to put a poster on the door of every second house, starting with the second house. The third volunteer puts a poster on the door of every third house, starting with the third house. This continues until the thousandth (and last) volunteer runs down the street and puts a single poster on the thousandth house.