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