Competitions

# Azerbaijan Programming Olympiad - 2nd Stage preparation

# Hands Shaking

Consider a meeting of **n** businessmen sitting around a circular table. To start the meeting, they must shake hands. Each businessman shakes the hand of exactly one other businessman. All handshakes happen simultaneously. We say that the shake is perfect if no arms cross each other.

Find the number of perfect shakes that exist for **n** businessmen.

** Input**

Each line contains one even integer **n** (**2** ≤ **n** ≤ **50**).

** Output**

For each value of **n** print in a separate line the number of perfect shakes that exist for **n** businessmen.

Input example #1

2 4 8

Output example #1

1 2 14