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