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