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(15, 2) :
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
15
2
1
0
0
1
1
2
↔
15
0
1
1
0
13
1
2
16
1
8
2
1
↔
15
1
8
1
0
14
1
2
8
2
8
7
Even
Even
1
4
3
7
1
1
4
1
8
6
0
2
12
2
12
3
Even
Even
1
6
4
3
1
1
6
1
8
2
0
2
14
2
14
1
Even
Even
1
7
5
1
1
1
7
1
8
0
6
1
1
1
7
1
8
0
7
1
1
1
7
1
8
0
(1)(15) - (7)(2) = 1