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, 4) :
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
4
1
0
0
1
1
4
↔
15
0
1
1
0
11
2
4
16
2
8
2
2
↔
15
2
8
1
0
13
1
Even
Even
1
4
3
1
↔
15
1
4
1
0
14
1
2
4
2
4
7
Even
Even
1
2
4
7
1
1
2
1
4
6
0
2
6
2
6
3
Even
Even
1
3
5
3
1
1
3
1
4
2
0
2
7
2
7
1
6
22
3
11
6
1
1
3
11
1
4
0
7
1
1
3
11
1
4
0
(3)(15) - (11)(4) = 1