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