hamming.py

import sys

def hamming(p1,p2,p3):
	yield 1

	for n in imerge( imult(p1, hamming(p1,p2,p3)), imerge( imult(p2, hamming(p1,p2,p3)), imult(p3, hamming(p1,p2,p3)) ) ):
		yield n

def imult(a, xs):
	x = xs.next()

	while True:
		yield a*x
		x = xs.next()

def imerge(xs, ys):
	x = xs.next()
	y = ys.next()

	while True:
		if x == y:
			yield x
			x = xs.next()
			y = ys.next()
		elif x < y:
			yield x
			x = xs.next()			
		else:
			yield y
			y = ys.next()

def hamming_i(p1,p2,p3,i):
	g = hamming(p1,p2,p3)
	for j in range(i+1):
		a = g.next()		
	return a



def main():
	if len(sys.argv) != 5:		
		print "hamming.py p1 p2 p3 i"
		raise SystemExit

	p1 = int(sys.argv[1])
	p2 = int(sys.argv[2])
	p3 = int(sys.argv[3])
	i  = int(sys.argv[4])

	print hamming_i(p1,p2,p3,i)

if __name__ == '__main__':	
	main()