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, 13) :
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
13
1
0
0
1
1
9
13
1
0
0
1
4
1
1
1
1
1
2
14
10
7
5
2
2
↔
9
7
5
1
0
7
1
20
14
10
7
3
1
↔
9
10
7
1
0
8
1
11
7
11
7
4
24
16
12
8
4
4
1
12
8
10
7
3
2
Even
Even
6
4
5
2
1
6
4
10
7
1
1
Even
Even
3
2
6
1
1
3
2
10
7
0
7
1
1
3
2
10
7
0
(3)(9) - (2)(13) = 1