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, 15) :
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
15
1
0
0
1
1
9
15
1
0
0
1
6
1
1
1
1
1
3
16
10
8
5
2
3
↔
9
8
5
1
0
6
1
9
5
9
5
3
24
14
12
7
3
3
3
12
7
8
5
0
4
3
3
12
7
8
5
0
5
3
3
12
7
8
5
0
6
3
3
12
7
8
5
0
7
3
3
12
7
8
5
0
(12)(9) - (7)(15) = 3