not interesting

fish.py

#!/usr/bin/env python2
# -*- coding: utf-8 -*-


from __future__ import print_function


num = raw_input("enter positive even number: ")
num = int(num)
result = 2
for i in xrange(4, num+2, 2): # xrange(start, stop, step) or "for (i=2, i<=num, i+=2) {}"
	result *= i

print("result:", result)