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(12, 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
12
13
1
0
0
1
1
12
13
1
0
0
1
1
6
14
12
7
6
2
6
13
7
6
0
1
7
3
20
18
10
9
3
3
13
10
9
0
1
10
1
10
10
10
10
5
Even
Even
5
5
4
5
↔
3
5
5
10
9
2
0
15
14
2
2
1
Even
Even
1
1
5
1
↔
3
1
1
10
9
2
1
11
10
11
10
1
24
22
12
11
6
1
1
12
11
1
1
0
7
1
1
12
11
1
1
0
(12)(12) - (11)(13) = 1