Pyramids

A pyramid of blocks is constructed by first building a base layer of n blocks and then adding n-1 blocks to the next layer. This process is repeated until the top layer only has one block.

You must calculate the number of blocks needed to construct a pyramid given the size of the base. For example, a pyramid that has a base of size 4 will need a total of 10 blocks.

The input will be a sequence of integers, one per line. The end of input will be signaled by the integer 0, and does not represent the base of a pyramid. All integers, other than the last (zero), are positive.

For each positive integer print the total number of blocks needed to build the pyramid with the specified base.