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