Algorithm title: UVA 991

Safe Salutations

Problem

As any minimally superstitious person knows all too, terriblethings'll happen when four persons do a crossed handsh Ake.

You, a intrepid computer scientist, are given the task of easing theburden of this people by providing and the them Sible set ofhandshakes that include everyone in the group while avoiding any suchcrossings. The following figure illustrates the case for 3 pairs ofpersons:

Input

The input to this problem contains several datasets separated by a blank line. Each dataset is simply a integern, the number ofpairs of people in the group, with 1≤ n ≤10.

Output

The output is equally simple. For each dataset, print a single integer indicating the numberof possible crossless handshakes this involve everyone in a GroupwithN pairs of people. Print a blank line between datasets.

Sample Input

4

Sample Output

14