Solve the following problem.

In the Asphalt Kingdom each city is connected to the other cities with a road of smooth blacktop. In order to make it simple for people to get around the Asphalt Kingdom there is a road connecting each city with all of the others. This happens for every city in the Asphalt Kingdom. For example, 10 years ago the Asphalt Kingdom only had 4 cities with 6 roads to connect them so there was a direct route from any city to any other city. Today the Asphalt Kingdom has grown to have 14 cities. How many roads does it have now? (D. Johanning, 1999)

Write a general expression that the King's Steamroller, can use to determine how many roads he will need to have for any number of cities.