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