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(13, 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
13
4
1
0
0
1
1
4
↔
13
0
1
1
0
9
2
4
14
2
7
2
2
↔
13
2
7
1
0
11
1
6
20
3
10
3
1
↔
13
3
10
1
0
12
1
4
10
4
10
6
Even
Even
2
5
4
6
1
2
5
3
10
5
3
6
18
3
9
5
3
1
3
9
3
10
2
0
6
19
2
6
1
Even
Even
1
3
6
1
1
1
3
3
10
0
7
1
1
1
3
3
10
0
(1)(13) - (3)(4) = 1