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