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