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