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