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(12, 9) :
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
12
9
1
0
0
1
1
12
9
1
0
0
1
3
6
10
12
5
6
2
6
9
5
6
0
1
3
3
14
18
7
9
3
3
9
7
9
0
1
6
1
7
10
7
10
3
16
22
8
11
4
3
↔
3
8
11
7
9
0
5
3
↔
3
8
11
7
9
0
6
3
↔
3
8
11
7
9
0
7
3
3
7
9
8
11
0
(7)(12) - (9)(9) = 3