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, 7) :
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
7
1
0
0
1
1
15
7
1
0
0
1
8
0
1
1
1
1
4
8
16
4
8
2
4
7
4
8
0
1
3
2
Even
Even
2
4
3
2
7
2
4
0
1
5
1
Even
Even
1
2
4
1
7
1
2
0
1
6
1
1
3
1
3
3
8
18
4
9
5
3
↔
1
4
9
1
2
2
0
5
11
5
11
1
12
26
6
13
6
1
↔
1
6
13
1
2
0
7
1
1
1
2
6
13
0
(1)(15) - (2)(7) = 1