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, 13) :
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
13
1
0
0
1
1
7
13
1
0
0
1
6
1
1
1
1
1
3
14
8
7
4
2
3
↔
7
7
4
1
0
4
1
8
4
8
4
2
Even
Even
4
2
3
2
3
4
2
7
4
1
1
Even
Even
2
1
4
1
3
2
1
7
4
2
1
9
5
9
5
1
22
12
11
6
5
1
↔
1
11
6
2
1
0
6
1
↔
1
11
6
2
1
0
7
1
1
2
1
11
6
0
(2)(7) - (1)(13) = 1