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, 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
15
13
1
0
0
1
1
15
13
1
0
0
1
2
0
1
1
1
1
1
14
16
7
8
2
1
13
7
8
0
1
12
1
7
9
7
9
6
20
24
10
12
3
6
↔
1
10
12
7
8
5
3
Even
Even
5
6
4
3
↔
1
5
6
7
8
2
0
12
14
12
14
1
Even
Even
6
7
5
1
↔
1
6
7
7
8
0
6
1
↔
1
6
7
7
8
0
7
1
1
7
8
6
7
0
(7)(15) - (8)(13) = 1