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