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(8, 15) :
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
8
15
1
0
0
1
1
8
15
1
0
0
1
7
4
16
8
8
4
2
4
15
8
4
0
1
11
2
Even
Even
4
2
3
2
15
4
2
0
1
13
1
Even
Even
2
1
4
1
15
2
1
0
1
14
1
2
2
2
2
7
Even
Even
1
1
5
7
↔
1
1
1
2
1
6
0
3
2
3
2
3
18
10
9
5
6
3
↔
1
9
5
2
1
2
0
11
6
11
6
1
26
14
13
7
7
1
1
2
1
13
7
0
(2)(8) - (1)(15) = 1