# numbtree1.py
# Written by Todd Wareham for CS 2500
"""
Given an integer n as a command-line argument, computes and prints the 
 number of unrooted binary trees with n leaves.

This version is implemented using the print statement's automatic number
 formatting.
"""

import sys

if (len(sys.argv) != 2):
    print "usage:", sys.argv[0], "n"
    sys.exit(1)

numBT = 1
for i in range(3, int(sys.argv[1]) + 1, 1):
    numBT *= ((2 * i) - 5)
print numBT