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(8, 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
8
13
1
0
0
1
1
8
13
1
0
0
1
5
4
14
8
7
4
2
4
13
7
4
0
1
9
2
20
12
10
6
3
2
13
10
6
0
1
11
1
Even
Even
5
3
4
1
13
5
3
0
1
12
1
5
4
5
4
6
18
12
9
6
5
6
↔
1
9
6
5
3
5
3
22
14
11
7
6
3
↔
1
11
7
5
3
2
0
16
10
3
2
1
16
10
8
5
7
1
1
5
3
8
5
0
(5)(8) - (3)(13) = 1