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