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, 6) :
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
6
1
0
0
1
1
6
↔
15
0
1
1
0
9
3
6
16
3
8
2
3
↔
15
3
8
1
0
12
1
4
8
4
8
6
Even
Even
2
4
3
6
3
2
4
3
8
3
3
Even
Even
1
2
4
3
3
1
2
3
8
0
5
3
3
1
2
3
8
0
6
3
3
1
2
3
8
0
7
3
3
1
2
3
8
0
(1)(15) - (2)(6) = 3