def progresivo(s, n, o):
	encoded = [ord(s[0]) + n,]
	decoded = [ord(s[0]) - n,]
	
	if o == 1:
		for i in s[1::]:
			encoded.append(ord(i) + encoded[-1])
		
		print "".join([unichr(x) for x in encoded])
	
	elif o == 0:
		for i in s[1::]:
			decoded.append(ord(i) - decoded[-1])
			
		print "".join([unichr(x) for x in decoded])

#Params: s = Texto a cifrar o descifrar | n = key | o = 1 -> cifrar, o = 0 -> descifrar
#progresivo('sanko', 2, 1) -> output example uÖńƯȞ