X =	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15
Y =	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15
X ↔ Y

Ext-GCD(2, 4) → Twos = 1 → Ext-GCD(1, 2) :

i	GCD			Bezout				AOdd :						AEven :
	A	↔	B	ax	ay	bx	by	|A-B|	A↔B	Sx	Sy	ax ← Sx'	ay ← Sy'	A ← A/2	ax ← ax + Y	ay ← ay + X	ax ← ax/2	ay ← ay/2
0	1		2	1	0	0	1
1	2	↔	1	0	1	1	0	1						1	2	2	1	1
2	1	↔	1	1	1	1	0	0
3	1	↔	1	1	1	1	0	0
4	1	↔	1	1	1	1	0	0
5	1	↔	1	1	1	1	0	0
6	1	↔	1	1	1	1	0	0
7	1		1	1	0	1	1	0
(1)(2) - (0)(4) = 2