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