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