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, 12) :
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
12
1
0
0
1
1
12
↔
13
0
1
1
0
1
6
12
14
6
7
2
6
↔
13
6
7
1
0
7
3
18
20
9
10
3
3
↔
13
9
10
1
0
10
1
10
10
10
10
5
Even
Even
5
5
4
5
3
5
5
9
10
2
0
14
15
2
2
1
Even
Even
1
1
5
1
3
1
1
9
10
2
1
10
11
10
11
1
22
24
11
12
6
1
↔
1
11
12
1
1
0
7
1
1
1
1
11
12
0
(1)(13) - (1)(12) = 1