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