Building and Checking an Identity Matrix

Every stage of Larkspur Labs' colour pipeline is described by a square table with one row and one column per channel. On start-up the pipeline runs a stage that changes nothing at all: the do-nothing table, which carries a 1 wherever a channel maps to itself and a 0 everywhere else. The self-test then reports a single figure from that table — the total of the entries lying on the line that runs from the table's top-left corner to its bottom-right corner — and the operator checks it against the channel count printed on the rig.

Task: Print the self-test figure for a do-nothing table of n channels.

Input

One line holding a single integer n, the number of channels.

Output

One line holding the self-test figure as a plain integer.

Example:

Input:
4

Output:
4